thank you all for the quick relies. Adding some more details on my findings: Constraining the interpreter to a version I know I don’t have locally (

==3.7.1

), from the output I could see the possible interpreters:

python3.6 CPython==3.6.12
python3.7 CPython==3.7.11
python3.7 CPython==3.7.7
python3.9 CPython==3.9.7
python3.8 CPython==3.8.9

Changed the constraint to

3.7.11

and it was possible to generate the lockfile either for

version A

and

version B

So this seems to suggest there is something going on indeed in the constraints relaxations on

pex

side. @hundreds-father-404 will follow your suggestion and run directly via

pex

, thanks. @enough-analyst-54434 my apologies, I am not sure if I followed. Both versions

A

and

B

have ranges on

python_requires

that should match interpreter constraint`["==3.7.*"]]` for any

>=3.7.1

, they overlap. Unless I am missing something.