Python modules not found in some tests

[mazunki]

Tests 5.4 and 8.4 are unable to run due to missing python modules:

Step 5.4 failed (nix-build ./unikernel.nix --argstr unikernel ./test/integration/kernel/kprint --arg doCheck true):

File "/nix/store/a75ma10zxr7z9ym9q5hcqphcq39s6d66-source/test.py", line 6, in <module>
    from past.utils import old_div
ModuleNotFoundError: No module named 'past'

👷⛔ Step 8.4 failed (nix-shell ./unikernel.nix --argstr unikernel ./test/integration/net/http --arg doCheck true):

  File "/home/maz/repos/includeos/IncludeOS/test/integration/net/http/test.py", line 3, in <module>
    from future import standard_library
ModuleNotFoundError: No module named 'future'

I'm not sure exactly when this started happening. I don't suppose it happened cuz of includeos/vmrunner#47... but rather it would be because of some changes in nixpkgs...? I thought we were pinning nixpkgs to avoid these issues, though.