Tests don't depend on external files

[jsignell]

Related Issue(s):

• closes Avoid network calls in tests suite #949, closes Make sure all test data is local #494

Description:

The vast majority of these changes have to do with validation so they might not be necessary if

PR Checklist:

• pre-commit hooks pass locally
• Tests pass (run scripts/test)
• Documentation has been updated to reflect changes, if applicable
• This PR maintains or improves overall codebase code coverage.
• Changes are added to the CHANGELOG. See the docs for information about adding to the changelog.

[jsignell]

Ok so apparently the cassettes depend on whether urllib3 is installed or not 🤦

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.01 ⚠️

Comparison is base (f9e5bd6) 91.99% compared to head (646d21e) 91.99%.

❗ Current head 646d21e differs from pull request most recent head d6913c2. Consider uploading reports for the commit d6913c2 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1162      +/-   ##
==========================================
- Coverage   91.99%   91.99%   -0.01%     
==========================================
  Files          51       51              
  Lines        6795     6792       -3     
  Branches     1000     1000              
==========================================
- Hits         6251     6248       -3     
  Misses        368      368              
  Partials      176      176              

Impacted Files	Coverage Δ
pystac/validation/local_validator.py	95.23% <100.00%> (-0.32%)	⬇️

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.