UnicodeDecodeError from pytest if object representation contains non-ascii, utf8 encoded, characters

[magopian]

Given the following test code:

    def test_foobar(self):
        class Foo(object):
            name = u'é'

            def __repr__(self):
                return self.name.encode('utf8')

        foo = Foo()
        assert not foo

Running it gives

Traceback (most recent call last):
  File "/Users/mathieu/olympia/apps/addons/tests/test_models.py", line 529, in test_foobar
    assert not foo
  File "/Users/mathieu/.virtualenvs/olympia/lib/python2.7/site-packages/_pytest/assertion/util.py", line 33, in format_explanation
    return u('\n').join(result)
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 11: ordinal not in range(128)

result is ['assert not \xc3\xa9']. I believe that python's default encoding used to decode from str to unicode is ascii, which fails while decoding the utf-8 encoded object representation.

[alvinchow86]

i'm seeing this issue too. FYI this is a duplicate of #678

[alvinchow86]

@RonnyPfannschmidt I did a similar fix here https://github.com/pytest-dev/pytest/compare/master...doordash:unicode-fix?expand=1, but I recall having to also fix some things in _format_lines() as well.