Drop support for Python 2

Is it still necessary to support Python 2? I would like to make CI/CD run tests on multiple Python versions and Python 2.7 seems to have same issues with depending packages, as seen in Job #3209.

DEPRECATION: Python 2.7 reached the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 is no longer maintained. A future version of pip will drop support for Python 2.7. More details about Python 2 support in pip, can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support