Fix lesson incrementing

[awjuliani]

Proposed change(s)

Fix issue with curriculum attempting to increment lesson even when there are no more lessons.

[Todo] I haven't added an additional test for this. I might need some help from someone more familiar with the curriculum codebase.

Useful links (Github issues, JIRA tickets, ML-Agents forum threads etc.)

Types of change(s)

• Bug fix
• New feature
• Code refactor
• Breaking change
• Documentation update
• Other (please describe)

Checklist

• Added tests that prove my fix is effective or that my feature works
• Updated the changelog (if applicable)
• Updated the documentation (if applicable)
• Updated the migration guide (if applicable)

Other comments

[vincentpierre]

Great catch !
I think we should even assert that the last lesson always has a None completion_criteria in this method

[ervteng]

Looks good and seconded Vince's comment

[chriselion]

Can you add a unit test that would have caught this before (or if you add the validation to completion_criteria, test that it fails)?

You might need to merge master to get the yamato tests passing again. Let me know if they're still failing after that and I'll take a look.

[awjuliani]

@vincentpierre Makes sense. The question is then how to handle this. My preference would be to just throw a warning and ignore the completion criteria of the last lesson, rather than throwing an error.

[vincentpierre]

My preference would be to just throw a warning and ignore the completion criteria of the last lesson, rather than throwing an error.

I agree.

[awjuliani]

Added a warning and a test to catch the user error originally reported.

[vincentpierre]

Not a must do for this PR, but to make sure your change worked, can you make a bunch of calls to param_manager.update_lessons to make sure it does not raise an error. (the error you fixed line 134 of environment_parameter_manager.py)

[awjuliani]

Added an explicit test for this.