Patch by Alex Gaynor.

TestHelpVersionOptional was redundant.

robust at shutdown. If needs to release multiple resources, they are released
even if errors are occured.

This will prevent failures from the version of NASM installed on buildbots,
if the ability to override the version used is desired again later, we can
figure out a way to opt in.

Patch by Davin Potts.

again if the first call to connect() raises an InterruptedError.

When the C function connect() fails with EINTR, the connection runs in
background. We have to wait until the socket becomes writable to be notified
when the connection succeed or fails.

Patch by Hoolean.

are down, don't use anymore in test_urllib2net

the FTP connection failed to fix a ResourceWarning.

returns bool.  tkinter.BooleanVar now validates input values (accepted bool,
int, str, and Tcl_Obj).  tkinter.BooleanVar.get() now always returns bool.

Patch by Makoto Kato.

the wait is cancelled, the future *fut* is now also cancelled.

@unittest.skipUnless(ssl, '...') doesn't work because the class body uses the
nntplib.NNTP_SSL attribute which doesn't exist.

Made test XML files non-ASCII.