Backports not properly ignored

Describe the bug

Even if I add --backport argparse to vermin, it still reports a minimum version requirement of Python 2.7.

To Reproduce

$ cat > foo.py
import argparse
$ vermin --backport argparse -vvvv foo.py
Detecting python files..
Analyzing using 4 processes..
2.7, 3.2     /Users/Adam/Downloads/foo.py
  L1 C7: 'argparse' requires 2.7, 3.2

Minimum required versions: 2.7, 3.2

Expected behavior

Any version of Python should work for this file.

Environment

• Vermin 0.10.4
• macOS 10.15.7
• Python 3.8.5

Additional information

If you have any trouble reproducing this, I suspect that this is a macOS + Python 3.8 bug. See https://docs.python.org/3.8/library/multiprocessing.html#contexts-and-start-methods:

Changed in version 3.8: On macOS, the spawn start method is now the default. The fork start method should be considered unsafe as it can lead to crashes of the subprocess. See bpo-33725.

One workaround would be to force it to always use the fork start method by replacing multiprocessing with multiprocessing.get_context('fork') everywhere it’s used. We recently had to do this for Spack: https://github.com/spack/spack/pull/18124

A more permanent workaround would be to ensure that both spawn and fork work as expected.

[netromdk]

That’s real easy. Will be sure to do that the next time around.

[adamjstewart]

Awesome, I added you.

Btw, in the future, if you cut a new release, you can add it to Spack by running:

$ spack checksum py-vermin 0.10.5

==> Fetching https://github.com/netromdk/vermin/archive/v0.10.5.tar.gz
####################################################################################### 100.0% 

    version('0.10.5', sha256='00601356e8e10688c52248ce0acc55d5b45417b462d5aa6887a6b073f0d33e0b')

Then run spack edit py-vermin and copy-n-paste that line into the package and submit a PR. Of course, I’m also happy to add new versions to the package as well, although I might not add new versions as regularly.