Python version isn't applied properly

[konstin]

requirements.txt:

-c package_constraints.txt

pytest-aiohttp==1.0.5

package_constraints.txt:

aiohttp==3.8.5;python_version<'3.12'
aiohttp==3.9.0b0;python_version>='3.12'

This fails on python 3.9:

  × No solution found when resolving dependencies:
  ╰─▶ Because pytest-aiohttp 1.0.5 depends on aiohttp ∅ and root 0a0.dev0 depends on pytest-aiohttp 1.0.5, root 0a0.dev0 is forbidden.

It passes when removing aiohttp==3.9.0b0;python_version>='3.12', even though the markers shouldn't match there anyway

Part of #199

[charliermarsh]

Good find, this is a good first issue. We need to filter constraints in the resolver's get_dependencies method (see iter_requirements for an example of how to filter requirements).

[charliermarsh]

\cc @zanieb if interested