chore: remove warnings for assertNotRegexpMatches method

[diegovr]

Description

Issue: openedx/public-engineering#157

• Replace the assertNotRegexpMatches with assertNotRegex method. This will remove the DeprecationWarning logs.

Supporting information

Python 3 renamed assertRegexpMatches to assertRegex, and assertNotRegexpMatches to assertNotRegex.

However, they did not add an alias for assertNotRegexpMatches until Python 3.5 (see https://docs.python.org/3/library/unittest.html#unittest.TestCase.assertNotRegex)

[openedx-webhooks]

Thanks for the pull request, @diegovr! Please note that it may take us up to several weeks or months to complete a review and merge your PR.

Feel free to add as much of the following information to the ticket as you can:

• supporting documentation
• Open edX discussion forum threads
• timeline information ("this must be merged by XX date", and why that is)
• partner information ("this is a course on edx.org")
• any other information that can help Product understand the context for the PR

All technical communication about the code itself will be done via the GitHub pull request interface. As a reminder, our process documentation is here.

Please let us know once your PR is ready for our review and all tests are green.

[diegovr]

@e0d could you please enable the tests to run

[diegovr]

Hi @e0d - The pipeline is 🟢.

[e0d]

@UsamaSadiq this PR was submitted based on an issue you authored. Are you the best reviewer?

[eLRuLL]

@UsamaSadiq could you please review this PR?

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX staging environment in preparation for a release to production.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.