Improve Python code: address unused variables (#11049)

* Address F841 (unused variable).

* Reformat.

* Add changelog fragment.

* More cleanup.

* Remove trailing whitespace.

* Readd removed code as a comment with TODO.

plugins/callback/elastic.py

@@ -145,7 +145,7 @@ class ElasticSource:
         self.host = socket.gethostname()
         try:
             self.ip_address = socket.gethostbyname(socket.gethostname())
-        except Exception as e:
+        except Exception:
             self.ip_address = None
         self.user = getpass.getuser()