OCW Courses with no year/semester fail to import

[ChristopherChudzicki]

Expected Behavior

Published OCW courses import successfully.

Current Behavior

Some fail. For example, https://ocw.mit.edu/courses/res-hs-002-chemistry-behind-the-magic-chemical-demonstrations-for-the-classroom/ fails to import.

Steps to Reproduce

In docker, run ./manage.py backpopulate_ocw_data --course-name=res-hs-002-chemistry-behind-the-magic-chemical-demonstrations-for-the-classroom. This results in an error:

ValueError: Field 'year' expected a number but got ''.

Possible Solution

Either:

• This: make the import script tolerate missing years (and semesters)
• or make the model property required and ensure all OCW courses have years / semesters
  • But it seems reasonable that https://ocw.mit.edu/courses/res-hs-002-chemistry-behind-the-magic-chemical-demonstrations-for-the-classroom/ does not have a year.

Confirmed with @pdpinch: Some "evergreen" OCW courses are expected to have no year/semesger

[mbertrand]

This will have an impact on #423