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>

test/conftest.py

@@ -6,7 +6,7 @@ import pytest
 @pytest.fixture(scope="module")
 def constants():
     # setup
-    class Constants(object):
+    class Constants:
         ONE = 1
         TWO = 2
     c = Constants()