~bzr-pqm/bzr/bzr.dev

2018.18.22 by Martin Pool
merge bzr.dev
1
# Copyright (C) 2006, 2007 Canonical Ltd
1534.4.50 by Robert Collins
Got the bzrdir api straightened out, plenty of refactoring to use it pending, but the api is up and running.
2
#   Authors: Robert Collins <robert.collins@canonical.com>
2018.18.22 by Martin Pool
merge bzr.dev
3
#            and others
1534.4.50 by Robert Collins
Got the bzrdir api straightened out, plenty of refactoring to use it pending, but the api is up and running.
4
#
5
# This program is free software; you can redistribute it and/or modify
6
# it under the terms of the GNU General Public License as published by
7
# the Free Software Foundation; either version 2 of the License, or
8
# (at your option) any later version.
9
#
10
# This program is distributed in the hope that it will be useful,
11
# but WITHOUT ANY WARRANTY; without even the implied warranty of
12
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13
# GNU General Public License for more details.
14
#
15
# You should have received a copy of the GNU General Public License
16
# along with this program; if not, write to the Free Software
17
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
18
19
"""Tests for the formatting and construction of errors."""
20
1948.1.6 by John Arbash Meinel
Make BzrNewError always return a str object
21
from bzrlib import (
22
    bzrdir,
23
    errors,
24
    )
25
from bzrlib.tests import TestCase, TestCaseWithTransport
1534.4.50 by Robert Collins
Got the bzrdir api straightened out, plenty of refactoring to use it pending, but the api is up and running.
26
27
2067.3.1 by Martin Pool
Clean up BzrNewError, other exception classes and users.
28
# TODO: Make sure builtin exception class formats are consistent - e.g. should
29
# or shouldn't end with a full stop, etc.
30
31
1534.4.50 by Robert Collins
Got the bzrdir api straightened out, plenty of refactoring to use it pending, but the api is up and running.
32
class TestErrors(TestCaseWithTransport):
33
2018.5.24 by Andrew Bennetts
Setting NO_SMART_VFS in environment will disable VFS methods in the smart server. (Robert Collins, John Arbash Meinel, Andrew Bennetts)
34
    def test_disabled_method(self):
35
        error = errors.DisabledMethod("class name")
36
        self.assertEqualDiff(
37
            "The smart server method 'class name' is disabled.", str(error))
38
2255.7.16 by John Arbash Meinel
Make sure adding a duplicate file_id raises DuplicateFileId.
39
    def test_duplicate_file_id(self):
40
        error = errors.DuplicateFileId('a_file_id', 'foo')
41
        self.assertEqualDiff('File id {a_file_id} already exists in inventory'
42
                             ' as foo', str(error))
43
2432.1.19 by Robert Collins
Ensure each HelpIndex has a unique prefix.
44
    def test_duplicate_help_prefix(self):
45
        error = errors.DuplicateHelpPrefix('foo')
46
        self.assertEqualDiff('The prefix foo is in the help search path twice.',
47
            str(error))
48
2550.2.3 by Robert Collins
Add require_api API.
49
    def test_incompatibleAPI(self):
50
        error = errors.IncompatibleAPI("module", (1, 2, 3), (4, 5, 6), (7, 8, 9))
51
        self.assertEqualDiff(
52
            'The API for "module" is not compatible with "(1, 2, 3)". '
53
            'It supports versions "(4, 5, 6)" to "(7, 8, 9)".',
54
            str(error))
55
2634.1.1 by Robert Collins
(robertc) Reinstate the accidentally backed out external_url patch.
56
    def test_in_process_transport(self):
57
        error = errors.InProcessTransport('fpp')
58
        self.assertEqualDiff(
59
            "The transport 'fpp' is only accessible within this process.",
60
            str(error))
61
1986.5.3 by Robert Collins
New method ``WorkingTree.flush()`` which will write the current memory
62
    def test_inventory_modified(self):
63
        error = errors.InventoryModified("a tree to be repred")
64
        self.assertEqualDiff("The current inventory for the tree 'a tree to "
65
            "be repred' has been modified, so a clean inventory cannot be "
66
            "read without data loss.",
67
            str(error))
68
2116.3.1 by John Arbash Meinel
Cleanup error tests
69
    def test_install_failed(self):
70
        error = errors.InstallFailed(['rev-one'])
71
        self.assertEqual("Could not install revisions:\nrev-one", str(error))
72
        error = errors.InstallFailed(['rev-one', 'rev-two'])
73
        self.assertEqual("Could not install revisions:\nrev-one, rev-two",
74
                         str(error))
75
        error = errors.InstallFailed([None])
76
        self.assertEqual("Could not install revisions:\nNone", str(error))
77
2255.2.145 by Robert Collins
Support unbreakable locks for trees.
78
    def test_lock_active(self):
79
        error = errors.LockActive("lock description")
80
        self.assertEqualDiff("The lock for 'lock description' is in use and "
81
            "cannot be broken.",
82
            str(error))
83
2535.3.4 by Andrew Bennetts
Simple implementation of Knit.insert_data_stream.
84
    def test_knit_data_stream_incompatible(self):
85
        error = errors.KnitDataStreamIncompatible(
86
            'stream format', 'target format')
87
        self.assertEqual('Cannot insert knit data stream of format '
88
                         '"stream format" into knit of format '
89
                         '"target format".', str(error))
90
2171.1.1 by John Arbash Meinel
Knit index files should ignore empty indexes rather than consider them corrupt.
91
    def test_knit_header_error(self):
92
        error = errors.KnitHeaderError('line foo\n', 'path/to/file')
93
        self.assertEqual("Knit header error: 'line foo\\n' unexpected"
2745.3.2 by Daniel Watkins
Updated tests to reflect new error text.
94
                         " for file \"path/to/file\".", str(error))
2171.1.1 by John Arbash Meinel
Knit index files should ignore empty indexes rather than consider them corrupt.
95
2196.2.5 by John Arbash Meinel
Add an exception class when the knit index storage method is unknown, and properly test for it
96
    def test_knit_index_unknown_method(self):
97
        error = errors.KnitIndexUnknownMethod('http://host/foo.kndx',
98
                                              ['bad', 'no-eol'])
99
        self.assertEqual("Knit index http://host/foo.kndx does not have a"
100
                         " known method in options: ['bad', 'no-eol']",
101
                         str(error))
102
2018.2.3 by Andrew Bennetts
Starting factoring out the smart server client "medium" from the protocol.
103
    def test_medium_not_connected(self):
104
        error = errors.MediumNotConnected("a medium")
105
        self.assertEqualDiff(
106
            "The medium 'a medium' is not connected.", str(error))
107
        
1534.4.50 by Robert Collins
Got the bzrdir api straightened out, plenty of refactoring to use it pending, but the api is up and running.
108
    def test_no_repo(self):
109
        dir = bzrdir.BzrDir.create(self.get_url())
110
        error = errors.NoRepositoryPresent(dir)
1740.5.6 by Martin Pool
Clean up many exception classes.
111
        self.assertNotEqual(-1, str(error).find((dir.transport.clone('..').base)))
112
        self.assertEqual(-1, str(error).find((dir.transport.base)))
1988.2.1 by Robert Collins
WorkingTree has a new api ``unversion`` which allow the unversioning of
113
        
2018.2.3 by Andrew Bennetts
Starting factoring out the smart server client "medium" from the protocol.
114
    def test_no_smart_medium(self):
115
        error = errors.NoSmartMedium("a transport")
116
        self.assertEqualDiff("The transport 'a transport' cannot tunnel the "
117
            "smart protocol.",
118
            str(error))
119
2432.1.4 by Robert Collins
Add an explicit error for missing help topics.
120
    def test_no_help_topic(self):
121
        error = errors.NoHelpTopic("topic")
122
        self.assertEqualDiff("No help could be found for 'topic'. "
123
            "Please use 'bzr help topics' to obtain a list of topics.",
124
            str(error))
125
1988.2.1 by Robert Collins
WorkingTree has a new api ``unversion`` which allow the unversioning of
126
    def test_no_such_id(self):
127
        error = errors.NoSuchId("atree", "anid")
2745.3.2 by Daniel Watkins
Updated tests to reflect new error text.
128
        self.assertEqualDiff("The file id \"anid\" is not present in the tree "
2745.3.3 by Daniel Watkins
Changed to remove need for escaping of quotes.
129
            "atree.",
1988.2.1 by Robert Collins
WorkingTree has a new api ``unversion`` which allow the unversioning of
130
            str(error))
1534.5.7 by Robert Collins
Start factoring out the upgrade policy logic.
131
1908.11.1 by Robert Collins
Add a new method ``Tree.revision_tree`` which allows access to cached
132
    def test_no_such_revision_in_tree(self):
133
        error = errors.NoSuchRevisionInTree("atree", "anid")
2745.3.3 by Daniel Watkins
Changed to remove need for escaping of quotes.
134
        self.assertEqualDiff("The revision id {anid} is not present in the"
135
                             " tree atree.", str(error))
1908.11.1 by Robert Collins
Add a new method ``Tree.revision_tree`` which allows access to cached
136
        self.assertIsInstance(error, errors.NoSuchRevision)
137
1986.5.3 by Robert Collins
New method ``WorkingTree.flush()`` which will write the current memory
138
    def test_not_write_locked(self):
139
        error = errors.NotWriteLocked('a thing to repr')
140
        self.assertEqualDiff("'a thing to repr' is not write locked but needs "
141
            "to be.",
142
            str(error))
143
2353.3.10 by John Arbash Meinel
Cleanup errors, and change ReadOnlyLockError to pass around more details.
144
    def test_read_only_lock_error(self):
145
        error = errors.ReadOnlyLockError('filename', 'error message')
146
        self.assertEqualDiff("Cannot acquire write lock on filename."
147
                             " error message", str(error))
148
2018.2.4 by Robert Collins
separate out the client medium from the client encoding protocol for the smart server.
149
    def test_too_many_concurrent_requests(self):
150
        error = errors.TooManyConcurrentRequests("a medium")
151
        self.assertEqualDiff("The medium 'a medium' has reached its concurrent "
152
            "request limit. Be sure to finish_writing and finish_reading on "
2018.5.134 by Andrew Bennetts
Fix the TooManyConcurrentRequests error message.
153
            "the currently open request.",
2018.2.4 by Robert Collins
separate out the client medium from the client encoding protocol for the smart server.
154
            str(error))
155
2245.1.3 by Robert Collins
Add install_hook to the BranchHooks class as the official means for installing a hook.
156
    def test_unknown_hook(self):
157
        error = errors.UnknownHook("branch", "foo")
158
        self.assertEqualDiff("The branch hook 'foo' is unknown in this version"
159
            " of bzrlib.",
160
            str(error))
161
        error = errors.UnknownHook("tree", "bar")
162
        self.assertEqualDiff("The tree hook 'bar' is unknown in this version"
163
            " of bzrlib.",
164
            str(error))
165
1534.5.7 by Robert Collins
Start factoring out the upgrade policy logic.
166
    def test_up_to_date(self):
167
        error = errors.UpToDateFormat(bzrdir.BzrDirFormat4())
1534.5.9 by Robert Collins
Advise users running upgrade on a checkout to also run it on the branch.
168
        self.assertEqualDiff("The branch format Bazaar-NG branch, "
169
                             "format 0.0.4 is already at the most "
170
                             "recent format.",
171
                             str(error))
1570.1.13 by Robert Collins
Check for incorrect revision parentage in the weave during revision access.
172
173
    def test_corrupt_repository(self):
174
        repo = self.make_repository('.')
175
        error = errors.CorruptRepository(repo)
176
        self.assertEqualDiff("An error has been detected in the repository %s.\n"
177
                             "Please run bzr reconcile on this repository." %
178
                             repo.bzrdir.root_transport.base,
179
                             str(error))
1948.1.6 by John Arbash Meinel
Make BzrNewError always return a str object
180
2052.6.1 by Robert Collins
``Transport.get`` has had its interface made more clear for ease of use.
181
    def test_read_error(self):
182
        # a unicode path to check that %r is being used.
183
        path = u'a path'
184
        error = errors.ReadError(path)
185
        self.assertEqualDiff("Error reading from u'a path'.", str(error))
186
2592.1.7 by Robert Collins
A validate that goes boom.
187
    def test_bad_index_format_signature(self):
188
        error = errors.BadIndexFormatSignature("foo", "bar")
189
        self.assertEqual("foo is not an index of type bar.",
190
            str(error))
2052.6.2 by Robert Collins
Merge bzr.dev.
191
2592.1.11 by Robert Collins
Detect truncated indices.
192
    def test_bad_index_data(self):
193
        error = errors.BadIndexData("foo")
194
        self.assertEqual("Error in data for index foo.",
195
            str(error))
196
2592.1.15 by Robert Collins
Detect duplicate key insertion.
197
    def test_bad_index_duplicate_key(self):
198
        error = errors.BadIndexDuplicateKey("foo", "bar")
199
        self.assertEqual("The key 'foo' is already in index 'bar'.",
200
            str(error))
201
2592.1.12 by Robert Collins
Handle basic node adds.
202
    def test_bad_index_key(self):
203
        error = errors.BadIndexKey("foo")
204
        self.assertEqual("The key 'foo' is not a valid key.",
205
            str(error))
206
2592.1.10 by Robert Collins
Make validate detect node reference parsing errors.
207
    def test_bad_index_options(self):
208
        error = errors.BadIndexOptions("foo")
209
        self.assertEqual("Could not parse options for index foo.",
210
            str(error))
211
2592.1.12 by Robert Collins
Handle basic node adds.
212
    def test_bad_index_value(self):
213
        error = errors.BadIndexValue("foo")
214
        self.assertEqual("The value 'foo' is not a valid value.",
215
            str(error))
216
2067.3.1 by Martin Pool
Clean up BzrNewError, other exception classes and users.
217
    def test_bzrnewerror_is_deprecated(self):
218
        class DeprecatedError(errors.BzrNewError):
219
            pass
2067.3.6 by Martin Pool
Update deprecation version
220
        self.callDeprecated(['BzrNewError was deprecated in bzr 0.13; '
2067.3.1 by Martin Pool
Clean up BzrNewError, other exception classes and users.
221
             'please convert DeprecatedError to use BzrError instead'],
222
            DeprecatedError)
223
224
    def test_bzrerror_from_literal_string(self):
225
        # Some code constructs BzrError from a literal string, in which case
226
        # no further formatting is done.  (I'm not sure raising the base class
227
        # is a great idea, but if the exception is not intended to be caught
228
        # perhaps no more is needed.)
229
        try:
230
            raise errors.BzrError('this is my errors; %d is not expanded')
231
        except errors.BzrError, e:
232
            self.assertEqual('this is my errors; %d is not expanded', str(e))
233
2018.2.4 by Robert Collins
separate out the client medium from the client encoding protocol for the smart server.
234
    def test_reading_completed(self):
235
        error = errors.ReadingCompleted("a request")
236
        self.assertEqualDiff("The MediumRequest 'a request' has already had "
237
            "finish_reading called upon it - the request has been completed and"
238
            " no more data may be read.",
239
            str(error))
240
241
    def test_writing_completed(self):
242
        error = errors.WritingCompleted("a request")
243
        self.assertEqualDiff("The MediumRequest 'a request' has already had "
244
            "finish_writing called upon it - accept bytes may not be called "
245
            "anymore.",
246
            str(error))
247
248
    def test_writing_not_completed(self):
249
        error = errors.WritingNotComplete("a request")
250
        self.assertEqualDiff("The MediumRequest 'a request' has not has "
251
            "finish_writing called upon it - until the write phase is complete"
252
            " no data may be read.",
253
            str(error))
254
2052.6.1 by Robert Collins
``Transport.get`` has had its interface made more clear for ease of use.
255
    def test_transport_not_possible(self):
256
        error = errors.TransportNotPossible('readonly', 'original error')
257
        self.assertEqualDiff('Transport operation not possible:'
258
                         ' readonly original error', str(error))
2052.4.4 by John Arbash Meinel
Create a SocketConnectionError to make creating nice errors easier
259
260
    def assertSocketConnectionError(self, expected, *args, **kwargs):
261
        """Check the formatting of a SocketConnectionError exception"""
262
        e = errors.SocketConnectionError(*args, **kwargs)
263
        self.assertEqual(expected, str(e))
264
265
    def test_socket_connection_error(self):
266
        """Test the formatting of SocketConnectionError"""
267
268
        # There should be a default msg about failing to connect
269
        # we only require a host name.
270
        self.assertSocketConnectionError(
271
            'Failed to connect to ahost',
272
            'ahost')
273
274
        # If port is None, we don't put :None
275
        self.assertSocketConnectionError(
276
            'Failed to connect to ahost',
277
            'ahost', port=None)
278
        # But if port is supplied we include it
279
        self.assertSocketConnectionError(
280
            'Failed to connect to ahost:22',
281
            'ahost', port=22)
282
283
        # We can also supply extra information about the error
284
        # with or without a port
285
        self.assertSocketConnectionError(
286
            'Failed to connect to ahost:22; bogus error',
287
            'ahost', port=22, orig_error='bogus error')
288
        self.assertSocketConnectionError(
289
            'Failed to connect to ahost; bogus error',
290
            'ahost', orig_error='bogus error')
291
        # An exception object can be passed rather than a string
292
        orig_error = ValueError('bad value')
293
        self.assertSocketConnectionError(
294
            'Failed to connect to ahost; %s' % (str(orig_error),),
295
            host='ahost', orig_error=orig_error)
296
297
        # And we can supply a custom failure message
298
        self.assertSocketConnectionError(
299
            'Unable to connect to ssh host ahost:444; my_error',
300
            host='ahost', port=444, msg='Unable to connect to ssh host',
301
            orig_error='my_error')
302
2376.4.26 by Jonathan Lange
Tests for MalformedBugIdentifier and new error UnknownBugTrackerAbbreviation.
303
    def test_malformed_bug_identifier(self):
304
        """Test the formatting of MalformedBugIdentifier."""
305
        error = errors.MalformedBugIdentifier('bogus', 'reason for bogosity')
306
        self.assertEqual(
307
            "Did not understand bug identifier bogus: reason for bogosity",
308
            str(error))
309
310
    def test_unknown_bug_tracker_abbreviation(self):
311
        """Test the formatting of UnknownBugTrackerAbbreviation."""
2376.4.27 by Jonathan Lange
Include branch information in UnknownBugTrackerAbbreviation
312
        branch = self.make_branch('some_branch')
313
        error = errors.UnknownBugTrackerAbbreviation('xxx', branch)
2376.4.26 by Jonathan Lange
Tests for MalformedBugIdentifier and new error UnknownBugTrackerAbbreviation.
314
        self.assertEqual(
2376.4.27 by Jonathan Lange
Include branch information in UnknownBugTrackerAbbreviation
315
            "Cannot find registered bug tracker called xxx on %s" % branch,
2376.4.26 by Jonathan Lange
Tests for MalformedBugIdentifier and new error UnknownBugTrackerAbbreviation.
316
            str(error))
2052.4.4 by John Arbash Meinel
Create a SocketConnectionError to make creating nice errors easier
317
2018.5.163 by Andrew Bennetts
Deal with various review comments from Robert.
318
    def test_unexpected_smart_server_response(self):
319
        e = errors.UnexpectedSmartServerResponse(('not yes',))
320
        self.assertEqual(
321
            "Could not understand response from smart server: ('not yes',)",
322
            str(e))
2052.4.4 by John Arbash Meinel
Create a SocketConnectionError to make creating nice errors easier
323
2506.2.1 by Andrew Bennetts
Start implementing container format reading and writing.
324
    def test_unknown_container_format(self):
325
        """Test the formatting of UnknownContainerFormatError."""
326
        e = errors.UnknownContainerFormatError('bad format string')
327
        self.assertEqual(
328
            "Unrecognised container format: 'bad format string'",
329
            str(e))
330
331
    def test_unexpected_end_of_container(self):
332
        """Test the formatting of UnexpectedEndOfContainerError."""
333
        e = errors.UnexpectedEndOfContainerError()
334
        self.assertEqual(
335
            "Unexpected end of container stream", str(e))
336
337
    def test_unknown_record_type(self):
338
        """Test the formatting of UnknownRecordTypeError."""
339
        e = errors.UnknownRecordTypeError("X")
340
        self.assertEqual(
341
            "Unknown record type: 'X'",
342
            str(e))
343
2506.3.1 by Andrew Bennetts
More progress:
344
    def test_invalid_record(self):
345
        """Test the formatting of InvalidRecordError."""
346
        e = errors.InvalidRecordError("xxx")
347
        self.assertEqual(
348
            "Invalid record: xxx",
349
            str(e))
350
2506.2.6 by Andrew Bennetts
Add validate method to ContainerReader and BytesRecordReader.
351
    def test_container_has_excess_data(self):
352
        """Test the formatting of ContainerHasExcessDataError."""
353
        e = errors.ContainerHasExcessDataError("excess bytes")
354
        self.assertEqual(
355
            "Container has data after end marker: 'excess bytes'",
356
            str(e))
357
2506.6.1 by Andrew Bennetts
Return a callable instead of a str from read, and add more validation.
358
    def test_duplicate_record_name_error(self):
359
        """Test the formatting of DuplicateRecordNameError."""
360
        e = errors.DuplicateRecordNameError(u"n\xe5me".encode('utf-8'))
361
        self.assertEqual(
2745.3.3 by Daniel Watkins
Changed to remove need for escaping of quotes.
362
            "Container has multiple records with the same name: n\xc3\xa5me",
2506.6.1 by Andrew Bennetts
Return a callable instead of a str from read, and add more validation.
363
            str(e))
2854.1.1 by Martin Pool
Fix "unprintable error" message for BzrCheckError and others
364
        
365
    def test_check_error(self):
366
        # This has a member called 'message', which is problematic in
367
        # python2.5 because that is a slot on the base Exception class
368
        e = errors.BzrCheckError('example check failure')
369
        self.assertEqual(
370
            "Internal check failed: example check failure",
371
            str(e))
372
        self.assertTrue(e.internal_error)
2506.6.1 by Andrew Bennetts
Return a callable instead of a str from read, and add more validation.
373
2535.3.40 by Andrew Bennetts
Tidy up more XXXs.
374
    def test_repository_data_stream_error(self):
375
        """Test the formatting of RepositoryDataStreamError."""
376
        e = errors.RepositoryDataStreamError(u"my reason")
377
        self.assertEqual(
378
            "Corrupt or incompatible data stream: my reason", str(e))
379
2116.3.1 by John Arbash Meinel
Cleanup error tests
380
2067.3.1 by Martin Pool
Clean up BzrNewError, other exception classes and users.
381
class PassThroughError(errors.BzrError):
382
    
383
    _fmt = """Pass through %(foo)s and %(bar)s"""
2116.3.1 by John Arbash Meinel
Cleanup error tests
384
385
    def __init__(self, foo, bar):
2067.3.1 by Martin Pool
Clean up BzrNewError, other exception classes and users.
386
        errors.BzrError.__init__(self, foo=foo, bar=bar)
387
388
389
class ErrorWithBadFormat(errors.BzrError):
390
391
    _fmt = """One format specifier: %(thing)s"""
392
393
394
class ErrorWithNoFormat(errors.BzrError):
395
    """This class has a docstring but no format string."""
2116.3.1 by John Arbash Meinel
Cleanup error tests
396
397
398
class TestErrorFormatting(TestCase):
399
    
400
    def test_always_str(self):
401
        e = PassThroughError(u'\xb5', 'bar')
402
        self.assertIsInstance(e.__str__(), str)
403
        # In Python str(foo) *must* return a real byte string
404
        # not a Unicode string. The following line would raise a
405
        # Unicode error, because it tries to call str() on the string
406
        # returned from e.__str__(), and it has non ascii characters
407
        s = str(e)
408
        self.assertEqual('Pass through \xc2\xb5 and bar', s)
409
2067.3.1 by Martin Pool
Clean up BzrNewError, other exception classes and users.
410
    def test_missing_format_string(self):
411
        e = ErrorWithNoFormat(param='randomvalue')
2067.3.3 by Martin Pool
merge bzr.dev and reconcile several changes, also some test fixes
412
        s = self.callDeprecated(
413
                ['ErrorWithNoFormat uses its docstring as a format, it should use _fmt instead'],
414
                lambda x: str(x), e)
415
        ## s = str(e)
416
        self.assertEqual(s, 
417
                "This class has a docstring but no format string.")
2067.3.1 by Martin Pool
Clean up BzrNewError, other exception classes and users.
418
2116.3.1 by John Arbash Meinel
Cleanup error tests
419
    def test_mismatched_format_args(self):
420
        # Even though ErrorWithBadFormat's format string does not match the
421
        # arguments we constructing it with, we can still stringify an instance
422
        # of this exception. The resulting string will say its unprintable.
423
        e = ErrorWithBadFormat(not_thing='x')
424
        self.assertStartsWith(
2067.3.1 by Martin Pool
Clean up BzrNewError, other exception classes and users.
425
            str(e), 'Unprintable exception ErrorWithBadFormat')