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/prserv/db.py

@@ -260,7 +260,7 @@ class PRData(object):
         self.connection.close()
 
     def __getitem__(self,tblname):
-        if not isinstance(tblname, basestring):
+        if not isinstance(tblname, str):
             raise TypeError("tblname argument must be a string, not '%s'" %
                             type(tblname))
         if tblname in self._tables: