I've updated the derivation with the new changes: https://gist.github.com/Slabity/34f82cdb7cf149483042a8fa530b75fd

Full error is the following:

Processing ./pytest-3.3.1-py2.py3-none-any.whl
Requirement already satisfied: py>=1.5.0 in /nix/store/3bjy7iw2si5yzn7wjzp0l9p5w7qaldax-python3.7-py-1.8.1/lib/python3.7/site-packages (from pytest==3.3.1) (1.8.1)
ERROR: Could not find a version that satisfies the requirement pluggy<0.7,>=0.5 (from pytest==3.3.1) (from versions: none)
ERROR: No matching distribution found for pluggy<0.7,>=0.5 (from pytest==3.3.1)
builder for '/nix/store/ymp94d5ipb0l4p88riqx86s8gbqx787z-python3.7-graphene-2.1.8.drv' failed with exit code 1
error: build of '/nix/store/ymp94d5ipb0l4p88riqx86s8gbqx787z-python3.7-graphene-2.1.8.drv' failed