Backport of the socketserver test, including output file (which is still
necessary in the 2.1 branch.) Guido's original checkin message:

A test suite for SocketServer.py that exposes the various bugs just
fixed.  Regrettably, this must be run manually -- somehow the I/O
redirection of the regression test breaks the test.  When run under
the regression test, this raises ImportError with a warning to that
effect.