Deprecation warnings for Python 3.4 and 3.5

[rtibbles]

Summary

• Sets up a logger with pretty colors for our env.py file (using the same color config as our regular logger)
• Adds a deprecation warning for Python versions 3.4 and 3.5 which gets logged as a warning and emitted as a Python warning

Reviewer guidance

Run kolibri with Python 3.4 and 3.5, confirm that a warning appears on the terminal.

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Testing checklist

• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical user journeys are covered by Gherkin stories
• Critical and brittle code paths are covered by unit tests

PR process

• PR has the correct target branch and milestone
• PR has 'needs review' or 'work-in-progress' label
• If PR is ready for review, a reviewer has been added. (Don't use 'Assignees')
• If this is an important user-facing change, PR or related issue has a 'changelog' label
• If this includes an internal dependency change, a link to the diff is provided

Reviewer checklist

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[jredrejo]

Looks good to me, tested with 2.7 & 3.8 without any issue