IP-254: Implement pytest coverage threshold of 95%.

[owenlittlejohns]

Description

Similar to this PR for earthdata-varinfo, this work implements a coverage threshold for the pytest unit test suite. For the test execution to succeed, the unit test coverage of the code in the earthdata_hashdiff directory must exceed 95%. It is currently at 98.64%.

Jira Issue ID

N/A - overdue IP sprint work.

Local Test Steps

• Pull this branch.
• Create a local Python environment.
• Install dependencies: pip install -r requirements.txt -r dev-requirements.txt -r tests/test_requirements.txt
• Run the tests using the updated pytest command: pytest --junitxml=tests/reports/earthdata-hashdiff_junit.xml --cov earthdata_hashdiff --cov-report html:tests/coverage --cov-report term --cov-fail-under=95 - you should see a logged message of meeting the required test coverage.
• Delete a couple test files. Then re-run the tests. When you have deleted enough test files, you will get below 95% code coverage, and see a logged message saying the coverage percentage is not reached.

PR Acceptance Checklist

• Acceptance criteria met
• Tests added/updated (if needed) and passing
• Documentation updated (if needed)
• CHANGELOG updated with the changes for this PR
• Package's __about__.py file changed if a new version should be published.

[flamingbear]

These are great changes.