anchor.diff:    };
   
     checkInputs = [
  -    pytestrunner pytest gunicorn async_generator pytest_xdist
  +    pytestrunner pytestCheckHook gunicorn async_generator pytest_xdist
       pytest-mock pytestcov trustme brotlipy freezegun
     ];
   
     propagatedBuildInputs = [ attrs chardet multidict async-timeout yarl ]
       ++ lib.optionals (pythonOlder "3.7") [ idna-ssl typing-extensions ];
   
  -  # disable tests which attempt to do loopback connections
  -  checkPhase = ''
  +  disabledTests = [
  +    # disable tests which attempt to do loopback connections
  +    "get_valid_log_format_exc"
  +    "test_access_logger_atoms"
  +    "aiohttp_request_coroutine"
  +    "server_close_keepalive_connection"
  +    "connector"
  +    "client_disconnect"
  +    "handle_keepalive_on_closed_connection"
  +    "proxy_https_bad_response"
  +    "partially_applied_handler"
  +    "middleware"
  +  ] ++ lib.optionals stdenv.is32bit [
  +    "test_cookiejar"
  +  ] ++ lib.optionals isPy38 [
  +    # Python 3.8  https://github.com/aio-libs/aiohttp/issues/4525
  +    "test_read_boundary_with_incomplete_chunk"
  +    "test_read_incomplete_chunk"
  +    "test_request_tracing_exception"
  +  ];
  +
  +  # aiohttp in current folder shadows installed version
  +  # Probably because we run `python -m pytest` instead of `pytest` in the hook.
  +  preCheck = ''
       cd tests
  -    pytest -k "not get_valid_log_format_exc \
  -               and not test_access_logger_atoms \
  -               and not aiohttp_request_coroutine \
  -               and not server_close_keepalive_connection \
  -               and not connector \
  -               and not client_disconnect \
  -               and not handle_keepalive_on_closed_connection \
  -               and not proxy_https_bad_response \
  -               and not partially_applied_handler \
  -               ${lib.optionalString stdenv.is32bit "and not test_cookiejar"} \
  -               and not middleware" \
  -      --ignore=test_connector.py
     '';
   
     meta = with lib; {
  
positive.code: , idna-ssl
  , typing-extensions
  , pytestrunner
  , pytest
  , gunicorn
  , pytest-timeout
  , async_generator
  
negative.code: , trustme
  , brotlipy
  , freezegun
  , isPy38
  }:
  
  buildPythonPackage rec {
    pname = "aiohttp";
    version = "3.6.2";
    # https://github.com/aio-libs/aiohttp/issues/4525 python3.8 failures
    disabled = pythonOlder "3.5";
  
    src = fetchPypi {
      inherit pname version;
  