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/version.py

@@ -68,12 +68,11 @@ def get_version(abbrev=4):
         if git_version != release_version:
             write_release_version(git_version)
         return git_version
-    elif release_version:
+    if release_version:
         return release_version
-    else:
-        raise ValueError('Cannot find a version number - make sure that '
-                         'git is installed or a RELEASE-VERSION file is '
-                         'present!')
+    raise ValueError('Cannot find a version number - make sure that '
+                     'git is installed or a RELEASE-VERSION file is '
+                     'present!')
 
 
 if __name__ == "__main__":