fix: deprecated urllib calls

[alespour]

Closes #602

Proposed Changes

Replaces deprecated urllib lib calls:

• HTTPResponse.getheaders() with HTTPResponse.headers`
• HTTPResponse.getheader(name, default) with HTTPResponse.headers.get(name, default)

Checklist

• [x] CHANGELOG.md updated
• [x] Rebased/mergeable
• [x] A test has been added if appropriate
• [x] pytest tests completes successfully
• [x] Commit messages are conventional

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 90.42%. Comparing base (0047fa9) to head (05e1bf2).

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #655 +/- ## ========================================== + Coverage 90.41% 90.42% +0.01% ========================================== Files 39 39 Lines 3505 3510 +5 ========================================== + Hits 3169 3174 +5 Misses 336 336 ```

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