'Test some special cases of [unicode] regexps.
One needs to use either r\'\' strings or write real `repr` of unicode strings, because of the following
(from python docs, http://docs.python.org/2/library/re.html):
\'for example, to match a literal backslash, one might have to write \'\\\\\' as the pattern string,
because the regular expression must be \\,
and each backslash must be expressed as \\ inside a regular Python string literal.\'
Example of real use case in Studio:
a) user inputs regexp in usual regexp language,
b) regexp is saved to xml and is read in python as repr of that string
So  a\d in front-end editor will become a\\\\d in xml,  so it will match a1 as student answer.'

def test_backslash_and_unicode_regexps(self):

    problem = self.build_problem(answer=u'5\\\\\xe6', case_sensitive=False, regexp=True)
    self.assert_grade(problem, u'5\\\xe6', 'correct')
    problem = self.build_problem(answer=u'5\\\\\xe6', case_sensitive=False, regexp=True)
    self.assert_grade(problem, u'5\\\xe6', 'correct')
