[BD-6] OPE-18 Compliance and Python 3.5 (3.8)

[ericfab179]

Update code with python-modernize to use python3. Update travis Ubuntu version. (Trusty to Xenial) Add setup.py install_requirements definition. Update travis file using new requirements. Create requirements folder. create pip_tools, base, dev, production, doc, test and travis requirements files. Remove old requirements file. Add Makefile. Add makefile upgrade command. Include requirements files generated using upgrade command. Remove old requirement files Update openedx.yaml. Add venv to gitignore. Update nltk constraint. Add aspell-en to apt packages. Add punkt nltk package to fix tests. Allow failures for python 3.8. This is necessary since travis is using python packages installed using apt, and this packages only work with default system python (For Xenial is python3.5).

Reviewers

• [ ] @awais786
• [ ] @morenol

[openedx-webhooks]

Thanks for the pull request, @ericfab179! I've created OSPR-4510 to keep track of it in JIRA. JIRA is a place for product owners to prioritize feature reviews by the engineering development teams.

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[openedx-webhooks]

@ericfab179 🎉 Your pull request was merged!

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