python: reformatted, fixed bugs

[pasabanov]

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• I have updated the documentation (in doc/) to reflect the changes made (if applicable)

#1447 #1449 #1984 #1986 #2113

Describe changes:

Reformatted Python scripts to match PEP.

Fixed mistake in class path: urllib.error.HTTPError.
The error module wasn't imported from urllib.

This problem has two solutions:

1. import urllib.error
2. Use urllib.request.HTTPError as HTTPError is importted from urllib.error in request.py.

I chose the second option as it is simpler.

[IvanNardi]

LGTM, thanks!