further fixes of py3 issues

complaints by pylint are mainly related to
- remove object from base list in class definitions
- unnecessary else/elif after return/raise

Change-Id: I13d15449149cc8bba0562338d0c9c42e97163bdf
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/21325
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

secop/features.py

@@ -28,9 +28,8 @@ from secop.metaclass import ModuleMeta
 from secop.modules import Command, Parameter
 
 
-class Feature(object, metaclass=ModuleMeta):
+class Feature(metaclass=ModuleMeta):
     """all things belonging to a small, predefined functionality influencing the working of a module"""
-    pass
 
 
 class HAS_PID(Feature):