test_urllib2.test_issue16464() fails randomly.

It uses http://www.example.com/ server.

Instead, I proposed to use http://httpbin.org/post URL which is written to support HTTP POST.

$ ./python -m test test_urllib2 -u all -v -m test_issue16464
======================================================================
ERROR: test_issue16464 (test.test_urllib2.MiscTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/vstinner/python/main/Lib/contextlib.py", line 155, in __exit__
    self.gen.throw(typ, value, traceback)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/vstinner/python/main/Lib/test/support/socket_helper.py", line 245, in transient_internet
    yield
    ^^^^^
  File "/home/vstinner/python/main/Lib/test/test_urllib2.py", line 1799, in test_issue16464
    opener.open(request, "1".encode("us-ascii"))
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/vstinner/python/main/Lib/urllib/request.py", line 525, in open
    response = meth(req, response)
               ^^^^^^^^^^^^^^^^^^^
  File "/home/vstinner/python/main/Lib/urllib/request.py", line 634, in http_response
    response = self.parent.error(
               ^^^^^^^^^^^^^^^^^^
  File "/home/vstinner/python/main/Lib/urllib/request.py", line 563, in error
    return self._call_chain(*args)
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/vstinner/python/main/Lib/urllib/request.py", line 496, in _call_chain
    result = func(*args)
             ^^^^^^^^^^^
  File "/home/vstinner/python/main/Lib/urllib/request.py", line 643, in http_error_default
    raise HTTPError(req.full_url, code, msg, hdrs, fp)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
urllib.error.HTTPError: HTTP Error 404: Not Found

Oh, bpo-46648 was already opened.