Enabling autograding in GH Classroom halts repository creation

[0xp4blo]

GitHub classroom assignments that have auto grading enabled produce multiple errors that prevents students from starting their submissions.

The errors occur in all sorts of configurations, i.e.: no starter code, starter code from template, starter code with source importer, i/o test, run command, etc.

There's no error message other than a never ending progress bar.

The error is solved when assignments are created without auto grading.

How to reproduce the error?

1. Create a new assignment with i/o test or run command grading method.
2. Use the assignment link to start a new submission.
3. Watch the process get stuck in either the "Creating repository" or "Importing started code" step.

Note: I initially though this issue was related with degraded performance in the import queue (education/classroom issues: 1772 & 1778).