Returns a list of Python version strings that
        the package has listed in :attr:`yarg.Release.classifiers`.

            >>> package = yarg.get('yarg')
            >>> package.python_versions
            [u'2.6', u'2.7', u'3.3', u'3.4']

def python_versions(self):
        """
        Returns a list of Python version strings that
        the package has listed in :attr:`yarg.Release.classifiers`.

            >>> package = yarg.get('yarg')
            >>> package.python_versions
            [u'2.6', u'2.7', u'3.3', u'3.4']
        """
        version_re = re.compile(r"""Programming Language \:\: """
                                """Python \:\: \d\.\d""")
        return [c.split(' :: ')[-1] for c in self.classifiers
                if version_re.match(c)]