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/layerindexlib/tests/restapi.py

@@ -112,7 +112,7 @@ class LayerIndexWebRestApiTest(LayersTest):
                     break
             else:
                 self.logger.debug(1, "meta-python was not found")
-                self.assetTrue(False)
+                raise self.failureException
 
             # Only check the first element...
             break