MAR-154: Drop suppor for Python 2.7 from the wsgi_website role:

- Mostly a matter of dropping the Python version parameter, and
updating some package versioning to account for Python 3 only.

MAR-151: Added support for Debian 10 Buster to wsgi_website role:

- Updated role reference documentaiton.
- Updated role meta information.
- Updated tests.
- Replace the installation of libmariadbclient-dev-compat library with
atftp - the actual package is differently named under Debian Stretch
and Debian Buster (which would complicate the test without any
benefits).
- Drop the fix for root mail alias in Vagrant image - seems it's no
longer a problem.
- Split-up the test for web application user since it's not possible
to keep it all under one parametrised test due to differences in
assigned system UID numbers for Debian Stretch and Debian Buster.
- Make the test for web application user less dependant on what the
actual UID number is in case of default value. By default user
should be created as system user, which means its UID number should
be less than 1000.

MAR-159: Set-up defaults for wsgi_requirements and update tests:

- Set defaults for the wsgi_requirements parameter (for running using
Python 2).
- Drop the use of futures_version and gunicorn_version from the
Molecule tests.
- Updated and deduplicated tests related to testing of
installed/requested futures and gunicorn package versions.

MAR-149: Switch to using File.content_string instead of File.content in tests for all roles:

- The .content variant returns contents as bytes, while the
content_string returns a string (which is what is wanted in
practically all cases).

MAR-148: Fixed the tests for wsgi_website role:

- Fix issues related to newlines in outputs.
- Refactor Python version check to make it more robust.

MAR-131: Added support for specifying Python version in wsgi_website role:

- Introduced additional role parameter for specifying the Python
version.
- Updated tests to verify new functionality.
- Fixed existing tests to account for differences between Python 2 and
Python 3 - including changes to WSGI test applications.
- Updated documentation, documenting new parameter and fixing one
minor typo.
- Updated release notes.
- Bumped default version of Gunicorn/futures used.

MAR-129: Updated wsgi_website role for Ansible 2.5.x and new Molecule:

- Include top-level linting configuration in test configuration file.
- Fixed linting errors.
- Updated Ansible deprecation warnings related to use of
state=installed with apt module.
- Updated how hosts are being referenced in tests.
- Rename the 'ss' utility in order to properly test socket
connectivity as a workaround for Testinfra bug.

MAR-128: Upgraded tests for ROLE_NAME role:

- Switch to new Molecule configuration.
- Updated set-up playbook to use become: yes.
- Moved some preparatory steps outside of the main playbook (eases
idempotence tests).
- Updated tests to reference the yml inventory file.
- Updated tests to use new fixture (host instead of individual ones).
- Switched to extracting hostname instead of hard-coding it in a
couple of tests.
- Fixed some linting issues.
- Updated one of the tests that depend on output of pip freeze due to
new versions of packages coming out.
- Updated hostname to include Debian version (for future expansion).
- Renamded some test data to match new hostname.