Expand io test coverage

[ghiggi]

Prework

• [x] I understand and agree to this repository's code of conduct.
• [x] I understand and agree to this repository's contributing guidelines.
• [x] I have already submitted an issue or discussion thread to discuss my idea with the maintainers.

What kind of change does this PR introduce? (check at least one)

• [x] Bugfix
• [ ] Feature
• [ ] Documentation
• [ ] Tutorial
• [ ] Code style update
• [ ] Refactor
• [ ] Build-related changes
• [ ] Other, please describe:

Does this PR introduce a breaking change? (check one)

• [ ] Yes
• [x] No

The PR fulfills these requirements:

• [ ] It's submitted to the branch named as follow :
  • Fix a bug: bugfix-<some_key>-<word>
  • Improve the doc: doc-<some_key>-<word>
  • Improve a tutorial tutorial-<some_key>-<word>
  • Add a new feature: feature-<some_key>-<word>
  • Refactor some code: refactor-<some_key>-<word>
  • Optimize some code: optimize-<some_key>-<word>
• [ ] When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• [ ] Don't forget to link PR to issue if you are solving one.
• [x] All tests are passing.
• [x] New/updated tests are included

I

[coveralls]

coverage: 64.695% (+3.0%) from 61.695% when pulling 25bc688448923b07b6209a4a793c1973151b052f on add_multiple_downloads into 59a1b48c57dcfcb82d0219e7660a54ac7fd929ed on main.

[codecov[bot]]

Codecov Report

Attention: 9 lines in your changes are missing coverage. Please review.

Comparison is base (59a1b48) 61.69% compared to head (25bc688) 64.69%.

Files	Patch %	Lines
gpm_api/io/ges_disc.py	57.14%	6 Missing :warning:
gpm_api/io/download.py	95.83%	2 Missing :warning:
gpm_api/io/checks.py	96.29%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #37 +/- ## ========================================== + Coverage 61.69% 64.69% +3.00% ========================================== Files 62 62 Lines 5498 5529 +31 ========================================== + Hits 3392 3577 +185 + Misses 2106 1952 -154 ```

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