[pgAdmin][SonarQube] Fixes for 13 rules.

Hi Hackers,

Attached is the patch to fix around 27 SonarQube related issues raised for
rules:

1. Remove this assignment to the local variable, the value is never used.
2. Rename local variables to match the regular expression
3. Add logic to this except clause or eliminate it and rethrow the
exception automatically.
4. Rename fields to match the regular expression
5. Extract this nested conditional expression into an independent
statement.
6. Change this default value to "None" and initialize this parameter
inside the function/method.
7. Update this function so that its implementation is not identical to
__repr__
8. Refactor this method to not always return the same value
9. Reraise this exception to stop the application as the user expects
10. Add missing parameters _w _PY3. This method overrides
simplejson.decoder.JSONDecoder.decode.
11. Remove this redundant continue.
12. Remove this unused function declaration
13. Remove this identity check; it will always be False.

Please review.

--
Thanks,
Aditya Toshniwal
pgAdmin hacker | Sr. Software Engineer | *edbpostgres.com*
<http://edbpostgres.com>
"Don't Complain about Heat, Plant a TREE"