anchor.diff:  }:
   
   let
  +  # Test whether the interpreter behaves in the different types of environments
  +  # we aim to support.
     environmentTests = let
       envs = let
         inherit python;
  
positive.code: { stdenv
  , python
  , runCommand
  
negative.code: 
    in lib.mapAttrs testfun envs;
  
    # Integration tests involving the package set.
    # All PyPy package builds are broken at the moment
    integrationTests = lib.optionalAttrs (python.pythonAtLeast "3.7"  && (!python.isPyPy)) rec {
      # Before the addition of NIX_PYTHONPREFIX mypy was broken with typed packages
  