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/metaclass.py

@@ -45,12 +45,12 @@ class ModuleMeta(PropertyMeta):
     and wraps read_*/write_* methods
     (so the dispatcher will get notfied of changed values)
     """
-    def __new__(mcs, name, bases, attrs):
+    def __new__(cls, name, bases, attrs):
         commands = attrs.pop('commands', {})
         parameters = attrs.pop('parameters', {})
         overrides = attrs.pop('overrides', {})
 
-        newtype = type.__new__(mcs, name, bases, attrs)
+        newtype = type.__new__(cls, name, bases, attrs)
         if '__constructed__' in attrs:
             return newtype