Update the HTTP 403 Error

[anmolsahoo25]

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Proposed changes

Updated the file retrieve code to get the files by adding the headers to the opener.

Types of changes

What types of changes does your code introduce? Put an x in the boxes that apply

• [x] 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

• [x ] I have read the CONTRIBUTING doc
• [x ] I agree to contribute my changes under the project's LICENSE
• [ x] I have checked that the unit tests pass locally with my changes
• [ x] I have checked the style of the new code (lint/pep).
• [x ] I have added tests that prove my fix is effective or that my feature works
• [ x] I have added necessary documentation (if appropriate)

Further comments

Reviewers

@rbrito

[coveralls]

Coverage decreased (-0.3%) to 47.7% when pulling f5ff8490330ace0de2b0413a3a7dd4f6a78fc859 on anmolsahoo25:fix-0-courses-available into b6c77a6e0a1735f7059412e8e09c356cbf693a6f on coursera-dl:fix-0-courses-available.