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/bin/bitbake-diffsigs

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # bitbake-diffsigs
 # BitBake task signature data comparison utility
@@ -24,6 +24,7 @@ import warnings
 import fnmatch
 import optparse
 import logging
+import pickle
 
 sys.path.insert(0, os.path.join(os.path.dirname(os.path.dirname(sys.argv[0])), 'lib'))
 
@@ -121,7 +122,6 @@ else:
     if len(args) == 1:
         parser.print_help()
     else:
-        import cPickle
         try:
             if len(args) == 2:
                 output = bb.siggen.dump_sigfile(sys.argv[1])