'Convert \'Foobar (1); baz\' to (\'Foobar ==1\', \'baz\')
Split environment marker, add == prefix to version specifiers as
necessary, and remove parenthesis.'

def _preparse_requirement(self, requires_dist):

    parts = (requires_dist.split(';', 1) + [''])
    distvers = parts[0].strip()
    mark = parts[1].strip()
    distvers = re.sub(self.EQEQ, '\\1==\\2\\3', distvers)
    distvers = distvers.replace('(', '').replace(')', '')
    return (distvers, mark)
