feat: add a default requires-python on import

[frostming]

Pull Request Check List

• A news fragment is added in news/ describing what is new.
• Test cases added for changed code.

Describe what you have changed in this PR.

Resolve #1416

[codecov-commenter]

Codecov Report

Base: 85.52% // Head: 85.53% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (61e314e) compared to base (dc5ee70).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1426   +/-   ##
=======================================
  Coverage   85.52%   85.53%           
=======================================
  Files          87       87           
  Lines        7571     7575    +4     
  Branches     1774     1775    +1     
=======================================
+ Hits         6475     6479    +4     
  Misses        714      714           
  Partials      382      382           

Flag	Coverage Δ
unittests	85.34% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/pdm/cli/actions.py	80.14% <100.00%> (+0.18%)	⬆️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.