assertion rewriting fails on bs4.element.Tag

beautiful-soup-assertion-rewriting.py

# vim: set fileencoding=utf-8 :

# related: https://bitbucket.org/hpk42/pytest/issue/453/assertion-rewriting-fails-with-object

#pip install beautifulsoup4

from bs4 import BeautifulSoup
def test_unicode():
    soup = BeautifulSoup('<b class="boldest">Б - Бага</b>')
    assert isinstance(soup.b, unicode)

pytest error

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
../venv/lib/python2.7/site-packages/_pytest/assertion/util.py:32: in format_explanation
    result = _format_lines(lines)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

lines = ['assert isinstance(<b class="boldest">\xd0\x91 - \xd0\x91\xd0\xb0\xd0\xb3\xd0\xb0</b>', '{<b class="boldest">\xd0\x91...x91\xd0\xb0\xd
0\xb3\xd0\xb0</b> = <b class="boldest">\xd0\x91 - \xd0\x91\xd0\xb0\xd0\xb3\xd0\xb0</b>.b', '}, unicode)']

    def _format_lines(lines):
        """Format the individual lines

        This will replace the '{', '}' and '~' characters of our mini
        formatting language with the proper 'where ...', 'and ...' and ' +
        ...' text, taking care of indentation along the way.

        Return a list of formatted lines.
        """
        result = lines[:1]
        stack = [0]
        stackcnt = [0]
        for line in lines[1:]:
            if line.startswith('{'):
                if stackcnt[-1]:
                    s = u('and   ')
                else:
                    s = u('where ')
                stack.append(len(result))
                stackcnt[-1] += 1
                stackcnt.append(0)
>               result.append(u(' +') + u('  ')*(len(stack)-1) + s + line[1:])
E               UnicodeDecodeError: 'ascii' codec can't decode byte 0xd0 in position 19: ordinal not in range(128)

../venv/lib/python2.7/site-packages/_pytest/assertion/util.py:104: UnicodeDecodeError
===================================================== 1 failed, 2 passed in 0.84 seconds ======================================================