Fix Python3.3 build

[bxsx]

Description of the change

Python 3.3 builds have started to fail when running python setup.py test that cannot retrieve 3rd party packages anymore.

This PR addresses this issue.

It also includes a minor refactor on using correct version of the mock package:
Install mock<=3.0.5 for Python 3.2- instead of Python 3.3- as unittest.mock has been added in Python3.3+

Type of change

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

Related issues

Fix [ch84510]

Checklists

Development

• Lint rules pass locally
• The code changed/added as part of this pull request has been covered with tests
• All tests related to the changed code pass in development

Code review

• This pull request has a descriptive title and information useful to a reviewer. There may be a screenshot or screencast attached
• "Ready for review" label attached to the PR and reviewers mentioned in a comment
• Changes have been reviewed by at least one other engineer
• Issue from task tracker has a link to this pull request

[shortcut-integration]

This pull request has been linked to Clubhouse Story #84510: Builds for Python3.3 with Flask/Django fail.