The importlib module must use real thread locks, not eventlet.Semaphore.

The os.open() function got a new option keyword-only dir_fd parameter in
Python 3.3:
https://docs.python.org/3/library/os.html#os.open

With this change, the open() now accepts the dir_fd parameter.

If it's determined that a MySQL test should be skipped during setUp(),
but after the parent setUp() has been called, having created and
started a timer, then tearDown() is never called and the timer never
cancelled, but left to expire during some future, unrelated test.

Move call to parent setUp() to end of child setUp() to insure that the
timer is only created and started after it's been determined that the
test shouldn't be skipped (ie create_db()).

https://github.com/eventlet/eventlet/pull/167
Signal socket bind to 127.0.0.1, '' does not work on Windows
sock.close() to fix ResourceWarning with python3 -Wd

Some error paths concatenate the output of "type" with a string,
which gives TypeError: cannot concatenate 'str' and 'type' objects,
rather than describing the actual error.

Closes #149 GH
Closes #150 GH

Conflicts:
	eventlet/hubs/twistedr.py

order in the class constructor so it uses the same order as the actual class
from Python 3.3 and above.

TimeoutExpired from Python 3.3 takes arguments in the following order:
cmd, timeout, output.

See https://github.com/python/cpython/blob/master/Lib/subprocess.py#L388