python3Packages.uvloop: enable on python3.8

Allow build pass by disabling test. Isolated issue to
test_sockets.py::TestAIOSockets::test_sock_close_add_reader_race.
This test is supposed to be skipped, but it isn't for some reason,
so we disable it instead.
See uvloop#284 (https://github.com/MagicStack/uvloop/pull/284)
for full details. Don't know why this test isn't properly skipped.

pkgs/development/python-modules/uvloop/default.nix

@@ -6,16 +6,17 @@
 , libuv
 , psutil
 , isPy27
-, pythonAtLeast
 , CoreServices
 , ApplicationServices
+# Check Inputs
+, pytestCheckHook
+# , pytest-asyncio
 }:
 
 buildPythonPackage rec {
   pname = "uvloop";
   version = "0.14.0";
-  # python 3.8 hangs on tests, assuming it's subtly broken with race condition
+  disabled = isPy27;
-  disabled = isPy27 || pythonAtLeast "3.8";
 
   src = fetchPypi {
     inherit pname version;
@@ -28,20 +29,44 @@ buildPythonPackage rec {
     libuv
   ] ++ lib.optionals stdenv.isDarwin [ CoreServices ApplicationServices ];
 
-  postPatch = ''
+  pythonImportsCheck = [
-    # Removing code linting tests, which we don't care about
+    "uvloop"
-    rm tests/test_sourcecode.py
+    "uvloop.loop"
-  '';
+  ];
 
-  checkInputs = [ pyopenssl psutil ];
+  dontUseSetuptoolsCheck = true;
+  checkInputs = [ pytestCheckHook pyopenssl psutil ];
+
+  pytestFlagsArray = [
+    # from pytest.ini, these are NECESSARY to prevent failures
+    "--capture=no"
+    "--assert=plain"
+    "--tb=native"
+    # ignore code linting tests
+    "--ignore=tests/test_sourcecode.py"
+  ];
+
+  disabledTests = [
+    "test_sock_cancel_add_reader_race"  # asyncio version of test is supposed to be skipped but skip doesn't happen. uvloop version runs fine
+  ];
+
+  # force using installed/compiled uvloop vs source by moving tests to temp dir
+  preCheck = ''
+    export TEST_DIR=$(mktemp -d)
+    cp -r tests $TEST_DIR
+    pushd $TEST_DIR
+  '';
+  postCheck = ''
+    popd
+  '';
 
   # Some of the tests use localhost networking.
   __darwinAllowLocalNetworking = true;
 
   meta = with lib; {
     description = "Fast implementation of asyncio event loop on top of libuv";
-    homepage = https://github.com/MagicStack/uvloop;
+    homepage = "https://github.com/MagicStack/uvloop";
     license = licenses.mit;
-    maintainers = [ maintainers.costrouc ];
+    maintainers = with maintainers; [ costrouc ];
   };
 }