Main tests failing due to codecov upload issue

See failing run: https://github.com/openedx/openedx-events/actions/runs/5379235047

Note: Rerunning failed tests resulted in the same issue.

Error:

[2023-06-26T14:16:11.168Z] ['info'] 
     _____          _
    / ____|        | |
   | |     ___   __| | ___  ___ _____   __
   | |    / _ \ / _` |/ _ \/ __/ _ \ \ / /
   | |___| (_) | (_| |  __/ (_| (_) \ V /
    \_____\___/ \__,_|\___|\___\___/ \_/

  Codecov report uploader 0.6.1
[2023-06-26T14:16:11.177Z] ['info'] => Project root located at: /home/runner/work/openedx-events/openedx-events
[2023-06-26T14:16:11.180Z] ['info'] -> No token specified or token is empty
[2023-06-26T14:16:11.187Z] ['info'] Searching for coverage files...
[2023-06-26T14:16:11.284Z] ['info'] Warning: Some files located via search were excluded from upload.
[2023-06-26T14:16:11.284Z] ['info'] If Codecov did not locate your files, please review https://docs.codecov.com/docs/supported-report-formats
[2023-06-26T14:16:11.284Z] ['info'] => Found 1 possible coverage files:
  coverage.xml
[2023-06-26T14:16:11.284Z] ['info'] Processing /home/runner/work/openedx-events/openedx-events/coverage.xml...
[2023-06-26T14:16:11.288Z] ['info'] Detected GitHub Actions as the CI provider.
[2023-06-26T14:16:11.941Z] ['info'] Pinging Codecov: https://codecov.io/upload/v4?package=github-action-3.1.4-uploader-0.6.1&token=*******&branch=main&build=5379235047&build_url=https%3A%2F%2Fgithub.com%2Fopenedx%2Fopenedx-events%2Factions%2Fruns%2F5379235047&commit=37a84a7228527e24848d7fae79c66e374e88f467&job=Python+CI&pr=&service=github-actions&slug=openedx%2Fopenedx-events&name=&tag=&flags=unittests&parent=
[2023-06-26T14:16:12.154Z] ['error'] There was an error running the uploader: Error uploading to [https://codecov.io:](https://codecov.io/) Error: There was an error fetching the storage URL during POST: 404 - {'detail': ErrorDetail(string='Unable to locate build via Github Actions API. Please upload with the Codecov repository upload token to resolve issue.', code='not_found')}
Error: Codecov: Failed to properly upload: The process '/home/runner/work/_actions/codecov/codecov-action/v3/dist/codecov' failed with exit code 255

Start with the failing GitHub Actions run 5379235047 and inspect the Python CI job using Codecov action v3. Review how coverage.xml is produced and how the upload is configured, especially the missing repository upload token. Done means the main tests and coverage upload complete successfully in GitHub Actions.