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/exceptions.py

@@ -86,6 +86,6 @@ def format_exception(etype, value, tb, context=1, limit=None, formatter=None):
 
 def to_string(exc):
     if isinstance(exc, SystemExit):
-        if not isinstance(exc.code, basestring):
+        if not isinstance(exc.code, str):
             return 'Exited with "%d"' % exc.code
     return str(exc)