Avogadro 2 has a plugin feature that allows for users to write command scripts using Python. This is actually how the input generators function, with the format for each program being specified in separate Python scripts.
The initial intention seems to have been to make it so these scripts would work for anyone with Python 3.5+. However, with the 2.0 release of Avogadro likely not occurring until at least the end of the year and Python 3.6 reaching end of life around this time, it may worth bumping up the minimum version. One major benefit of this would the inclusion of f-strings, which were introduced in Python 3.6 and are very convenient for formatting text.
To make this change, it would be useful to know what version of Python people use on their computers, to avoid a case where the minimum version is set higher than what most people actually use. This was mentioned on a couple open pull-requests on the avogenerators Github. Personally, I have different versions across different computers, but I think all of them are at least up to Python 3.7. I think this would be a reasonable minimum version, as it is likely a lot of users are at least up to this version and it has features like f-strings that would make it more convenient than 3.5.