Keep test_main() and remove subTest() (introduced in Python 3.4).

… (#2291)

The current regex based splitting produces a wrong result. For example::

  http://abc#@def

Web browsers parse that URL as ``http://abc/#@def``, that is, the host
is ``abc``, the path is ``/``, and the fragment is ``#@def``.
(cherry picked from commit 90e01e5)
(cherry picked from commit cc54c1c)