edx problems download

[kyilmaz80]

🚨Please review the guidelines for contributing to this repository.

Proposed changes

It is a new feature. Some courses have more useful information than videos like problems. One can want to download problems like me. So I added minimal code changes to accomplish this task.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating
the PR. If you're unsure about any of them, don't hesitate to ask. We're here
to help! This is simply a reminder of what we are going to look for before
merging your code.

• I have read the CONTRIBUTING doc
• I agree to contribute my changes under the project's LICENSE
• I have checked that the unit tests pass locally with my changes
  I added my credentials to test_failed_login() function and change the assertion to overcome the
  coverage analysis script. Because test_failed_login() returns HTTP 400 and no resp object occurs.
• I have checked the style of the new code (lint/pep).
• I have added tests that prove my fix is effective or that my feature works
  I tested with various edx sites and see the html problem pages.
• I have added necessary documentation (if appropriate)

Further comments

Reviewers

[floviolleau]

Hi @rbrito,

Can you please merge this PR?

Thanks