bitbake: lib: fix most undefined code picked up by pylint

Correctly import, and inherit functions, and variables.
Also fix some typos and remove some Python 2 code that isn't recognised.

(Bitbake rev: b0c807be5c2170c9481c1a04d4c11972135d7dc5)

Signed-off-by: Frazer Clews <frazerleslieclews@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/hashserv/tests.py

@@ -9,6 +9,7 @@ from . import create_server, create_client
 import hashlib
 import logging
 import multiprocessing
+import os
 import sys
 import tempfile
 import threading