anchor.diff:  { buildPythonPackage
   , fetchFromGitHub
   , lib
  -, black
   , graphql-core
   , promise
   , fetchpatch
   , pythonOlder
  +, pytestCheckHook
   }:
   
   buildPythonPackage rec {
     pname = "graphql-server-core";
     version = "2.0.0";
  +  disable = pythonOlder "3.6";
   
     src = fetchFromGitHub {
       owner = "graphql-python";
  
positive.code:     rev = "v${version}";
      sha256 = "1w3biv2za2m1brwjy0z049c2m94gm1zfwxzgc6lwrsci724jv9fr";
    };
  
    disable = pythonOlder "3.6";
  
    patches = [
      (fetchpatch {
  
negative.code:     promise
    ];
  
    # fail with: cannot import name 'format_error' from 'graphql'
    doCheck = false;
  
    checkInputs = [
      pytestCheckHook
    ];
  
    meta = with lib; {
      description = "Core package for using GraphQL in a custom server easily";
      homepage = "https://github.com/graphql-python/graphql-server-core";
      license = licenses.mit;
      maintainers = with maintainers; [ kamadorueda ];
    };
  }
  