Minimum python version

[jebrosen]

Currently polyA requires Python 3.8 or newer. Many of our potential users normally have access to an LTS or stale release of a Linux distribution which will perpetually be a few steps behind the current python release; a few examples:

• Debian oldstable (currently Debian 10 "buster"): python 3.7
• CentOS 7: python 3.6

One solution to this problem is to install python through a user-level package manager, such as bioconda. But if supporting python 3.4 or 3.6 is not too much of a burden, it would be one less thing for users to worry about.

So far I have found only a few things that are not available in python 3.6: typing.Literal was added in 3.8, and subprocess.run() has a few convenience arguments (capture_output, text) which were added in 3.7 as aliases for other older parameters (stdout, stderr, universal_newlines).