Improve senza/error_handling.py based on pylint

[jmcs]

• Docstrings;
• More specific variable names;
• Reduced some code repetition;

There are still a couple of warnings because sentry is constant but lower case, the catch-all except and the typing imports.

[coveralls]

Coverage remained the same at 89.753% when pulling 40609d4 on pylint-friday-4 into d5be62f on master.

[rafaelcaricio]

👍