bitbake: bitbake: Convert to python 3

Various misc changes to convert bitbake to python3 which don't warrant
separation into separate commits.

(Bitbake rev: d0f904d407f57998419bd9c305ce53e5eaa36b24)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/checksum.py

@@ -19,20 +19,13 @@ import glob
 import operator
 import os
 import stat
+import pickle
 import bb.utils
 import logging
 from bb.cache import MultiProcessCache
 
 logger = logging.getLogger("BitBake.Cache")
 
-try:
-    import cPickle as pickle
-except ImportError:
-    import pickle
-    logger.info("Importing cPickle failed. "
-                "Falling back to a very slow implementation.")
-
-
 # mtime cache (non-persistent)
 # based upon the assumption that files do not change during bitbake run
 class FileMtimeCache(object):