def test_opt_charsetEndOfLine(self):
        """
        A line that ends with a C{CHARSET} identifier is parsed as
        that identifier, and the remainder is the empty string.
        """
        line = b"CHARSET UTF-8"
        identifier, remainder = self.server.opt_charset(line)
        self.assertEqual(identifier, b"UTF-8")
        self.assertEqual(remainder, b"")

        A line that ends with a C{CHARSET} identifier is parsed as
        that identifier, and the remainder is the empty string.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/test/test_imap.py