if not self.unicode_literals and val[0] in '\'"' and '\\' in val:
    val = '\\\\'.join([v.replace('\\u', '\\\\u').replace('\\U', '\\\\U') for
        v in val.split('\\\\')])
if val[0] in 'uU':
    val = val[1:]
if val == node.value:
    pass
2to3 says "No changes needed", then "files that need to be modified"