multiple exceptions can lose too much context

[Robert Collins]

I had this test code:

        fixture = self.useFixture(command.get_run_command())

and when it blew up like so:

======================================================================
ERROR: testrepository.tests.test_testcommand.TestTestCommand.test_list_tests_multiple_profiles
----------------------------------------------------------------------
traceback-1: {{{
Traceback (most recent call last):
  File "/home/robertc/.virtualenvs/scratch/local/lib/python2.7/site-packages/fixtures/fixture.py", line 208, in setUp
    raise SetupError(details)
fixtures.fixture.SetupError: {}
}}}

Traceback (most recent call last):
  File "/home/robertc/.virtualenvs/scratch/local/lib/python2.7/site-packages/fixtures/fixture.py", line 197, in setUp
    self._setUp()
  File "testrepository/testcommand.py", line 246, in _setUp
    self._instance = self._instance_source.obtain_instance(self._profile)
  File "testrepository/testcommand.py", line 845, in obtain_instance
    out = out.decode('utf-8')
  File "/home/robertc/.virtualenvs/scratch/lib/python2.7/encodings/utf_8.py", line 16, in decode
    return codecs.utf_8_decode(input, errors, True)
UnicodeDecodeError: 'utf8' codec can't decode byte 0xb3 in position 0: invalid start byte

I couldn't tell where the failure was coming from. I haven't dug into what frame hiding was going on.

[Robert Collins (lifeless)]

The raw stacks:
(Pdb) sys.modules['traceback2'].print_tb(exc_info[1][0][2])
  File "/home/robertc/.virtualenvs/scratch/local/lib/python2.7/site-packages/fixtures/fixture.py", line 197, in setUp
    self._setUp()
  File "testrepository/testcommand.py", line 246, in _setUp
    self._instance = self._instance_source.obtain_instance(self._profile)
  File "testrepository/testcommand.py", line 845, in obtain_instance
    out = out.decode('utf-8')
  File "/home/robertc/.virtualenvs/scratch/lib/python2.7/encodings/utf_8.py", line 16, in decode
    return codecs.utf_8_decode(input, errors, True)
(Pdb) sys.modules['traceback2'].print_tb(exc_info[1][1][2])
  File "/home/robertc/.virtualenvs/scratch/local/lib/python2.7/site-packages/fixtures/fixture.py", line 208, in setUp
    raise SetupError(details)

Which suggests we're trimming too much inside of fixtures, perhaps.

[Robert Collins (lifeless)]

(Pdb) sys.modules['traceback2'].print_tb(exc_info[2])
  File "/home/robertc/.virtualenvs/scratch/local/lib/python2.7/site-packages/testtools/testcase.py", line 666, in useFixture
    fixture.setUp()
  File "testrepository/testcommand.py", line 469, in setUp
    self.test_ids = self.list_tests(self._instance_source.default_profiles)
  File "testrepository/testcommand.py", line 519, in list_tests
    ids = self._list_tests(profile)
  File "testrepository/testcommand.py", line 531, in _list_tests
    self.ui, self._instance_source, self._parser, profile) as runner:
  File "/home/robertc/.virtualenvs/scratch/local/lib/python2.7/site-packages/fixtures/fixture.py", line 152, in __enter__
    self.setUp()
  File "/home/robertc/.virtualenvs/scratch/local/lib/python2.7/site-packages/fixtures/fixture.py", line 212, in setUp
    raise MultipleExceptions(*errors)

so we're missing the frame that called into the fixture at this step. But - its also raising M.E., so I need to dig more.

[Robert Collins (lifeless)]

And here's the first error at the first except -
(Pdb) sys.modules['traceback2'].print_tb(err[2])
  File "/home/robertc/.virtualenvs/scratch/local/lib/python2.7/site-packages/fixtures/fixture.py", line 197, in setUp
    self._setUp()
  File "testrepository/testcommand.py", line 246, in _setUp
    self._instance = self._instance_source.obtain_instance(self._profile)
  File "testrepository/testcommand.py", line 845, in obtain_instance
    out = out.decode('utf-8')
  File "/home/robertc/.virtualenvs/scratch/lib/python2.7/encodings/utf_8.py", line 16, in decode
    return codecs.utf_8_decode(input, errors, True)

...
and here it is:
(Pdb) sys.modules['traceback2'].print_stack(err[2].tb_frame)
  File "/usr/lib/python2.7/runpy.py", line 162, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/lib/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/home/robertc/.virtualenvs/scratch/lib/python2.7/site-packages/testtools/run.py", line 267, in <module>
    main(sys.argv, sys.stdout)
  File "/home/robertc/.virtualenvs/scratch/lib/python2.7/site-packages/testtools/run.py", line 264, in main
    stdout=stdout)
  File "/home/robertc/.virtualenvs/scratch/lib/python2.7/site-packages/testtools/run.py", line 187, in __init__
    self.runTests()
  File "/home/robertc/.virtualenvs/scratch/lib/python2.7/site-packages/testtools/run.py", line 221, in runTests
    self.result = testRunner.run(self.test)
  File "/home/robertc/.virtualenvs/scratch/lib/python2.7/site-packages/testtools/run.py", line 107, in run
    return test.run(result)
  File "/usr/lib/python2.7/unittest/suite.py", line 108, in run
    test(result)
  File "/home/robertc/.virtualenvs/scratch/local/lib/python2.7/site-packages/unittest2/suite.py", line 87, in __call__
    return self.run(*args, **kwds)
  File "/home/robertc/.virtualenvs/scratch/local/lib/python2.7/site-packages/unittest2/suite.py", line 126, in run
    test(result)
  File "/usr/lib/python2.7/unittest/suite.py", line 70, in __call__
    return self.run(*args, **kwds)
  File "/home/robertc/.virtualenvs/scratch/local/lib/python2.7/site-packages/testresources/__init__.py", line 260, in run
    test(result)
  File "/home/robertc/.virtualenvs/scratch/local/lib/python2.7/site-packages/unittest2/case.py", line 673, in __call__
    return self.run(*args, **kwds)
  File "/home/robertc/.virtualenvs/scratch/local/lib/python2.7/site-packages/testtools/testcase.py", line 606, in run
    return run_test.run(result)
  File "/home/robertc/.virtualenvs/scratch/local/lib/python2.7/site-packages/testtools/runtest.py", line 80, in run
    return self._run_one(actual_result)
  File "/home/robertc/.virtualenvs/scratch/local/lib/python2.7/site-packages/testtools/runtest.py", line 94, in _run_one
    return self._run_prepared_result(ExtendedToOriginalDecorator(result))
  File "/home/robertc/.virtualenvs/scratch/local/lib/python2.7/site-packages/testtools/runtest.py", line 108, in _run_prepared_result
    self._run_core()
  File "/home/robertc/.virtualenvs/scratch/local/lib/python2.7/site-packages/testtools/runtest.py", line 144, in _run_core
    self.case._run_test_method, self.result):
  File "/home/robe...

[Jonathan Lange (jml)]

Related to #1188420 perhaps?