The behavior of `autopep8` differs between older and newer versions.
Enforcing a minimum version is an attempt to enforce the same rules for
everybody, avoiding code conflicts coming to the linter.
The minimum version is selected as being the minimum version shipped
with these OSs:
- Ubuntu 18.04 (Ubuntu 16.04 version is older but can be easily
updated)
- Debian Sid
- FreeBSD 12.0
- OSX 10.12 Sierra