Protect against buggy participants reports from Aalto SISU API

[ihalaij1]

Description

What?

It has turned out that Aalto's SISU API gateway occasionally returns an empty list for all courses queried using this API because of some malfunction. This causes all students to be removed from course enrollments (and a major hassle as a result). Therefore we have now added a check to the code to protect against this situation: if the response contains an empty participant list, it is ignored.

Additionally, the error handling now reports the error code more clearly in logs.

Fixes #1180

Testing

What type of test did you run?

• Accessibility test using the WAVE extension.
• Django unit tests.
• Selenium tests.
• Other test. (Add a description below)
• Manual testing.

This fix was not tested, because of the difficulty of doing that, but I assume there are no problems.

Did you test the changes in

• Chrome
• Firefox
• This pull request cannot be tested in the browser.

Programming style

• Did you follow our style guides?
• Did you use Python type hinting in all functions that you added or edited? (type hints for function parameters and return values)

Have you updated the README or other relevant documentation?

• documents inside the doc directory.
• README.md.
• Aplus Manual.
• Other documentation (mention below which documentation).

Is it Done?

• Reviewer has finished the code review
• After the review, the developer has made changes accordingly
• Customer/Teacher has accepted the implementation of the feature

[PasiSa]

Couple of change proposal related to logging. What do you think?

[ihalaij1]

Couple of change proposal related to logging. What do you think?

I made the suggested changes!

[PasiSa]

Thanks, looks good to me.

[markkuriekkinen]

Well done! I have one preference, though. I like to include a bit more background in the git commit message. If there is only a link to the issue, then you have to open the issue to remember what the problem really was.

I will merge this now.