python3Packages.SQLAlchemy: don't run tests in parallel

Test failures on hydra look suspiciously like they stem from xdist.

gw0 ok / gw1 ok / gw2 ok / gw3 ok / gw4 ok / gw5 ok / gw6 ok / gw7 ok / gw8 ok / gw9 ok / gw10 ok / gw11 ok / gw12 ok / gw13 ok / gw14 ok / gw15 ok / gw16 ok / gw17 ok / gw18 ok / gw19 C / gw20 C / gw21 C / gw22 C / gw23 C / gw24 C / gw25 C / gw26 C / gw27 C / gw28 C / gw29 C / gw30 C / gw31 C / gw32 C / gw33 C / gw34 C / gw35 C / gw36 C / gw37 C / gw38 C / gw39 C / gw40 C / gw41 C / gw42 C / gw43 C / gw44 C / gw45 C / gw46 C / gw47 CINTERNALERROR> def worker_internal_error(self, node, formatted_error):
INTERNALERROR>         """
INTERNALERROR>         pytest_internalerror() was called on the worker.
INTERNALERROR>
INTERNALERROR>         pytest_internalerror() arguments are an excinfo and an excrepr, which can't
INTERNALERROR>         be serialized, so we go with a poor man's solution of raising an exception
INTERNALERROR>         here ourselves using the formatted message.
INTERNALERROR>         """
INTERNALERROR>         self._active_nodes.remove(node)
INTERNALERROR>         try:
INTERNALERROR> >           assert False, formatted_error
INTERNALERROR> E           AssertionError: Traceback (most recent call last):
INTERNALERROR> E               File "/nix/store/4v6lhz8sq9jwl3af8abs6cgpbh9lignr-python3.8-pytest-6.2.3/lib/python3.8/site-packages/_pytest/main.py", line 267, in wrap_session
INTERNALERROR> E                 config.hook.pytest_sessionstart(session=session)
INTERNALERROR> E               File "/nix/store/r4lwmmknxwx3gq2bv73yf0rkli9d902d-python3.8-pluggy-0.13.1/lib/python3.8/site-packages/pluggy/hooks.py", line 286, in __call__
INTERNALERROR> E                 return self._hookexec(self, self.get_hookimpls(), kwargs)
INTERNALERROR> E               File "/nix/store/r4lwmmknxwx3gq2bv73yf0rkli9d902d-python3.8-pluggy-0.13.1/lib/python3.8/site-packages/pluggy/manager.py", line 93, in _hookexec
INTERNALERROR> E                 return self._inner_hookexec(hook, methods, kwargs)
INTERNALERROR> E               File "/nix/store/r4lwmmknxwx3gq2bv73yf0rkli9d902d-python3.8-pluggy-0.13.1/lib/python3.8/site-packages/pluggy/manager.py", line 84, in <lambda>
INTERNALERROR> E                 self._inner_hookexec = lambda hook, methods, kwargs: hook.multicall(
INTERNALERROR> E               File "/nix/store/r4lwmmknxwx3gq2bv73yf0rkli9d902d-python3.8-pluggy-0.13.1/lib/python3.8/site-packages/pluggy/callers.py", line 208, in _multicall
INTERNALERROR> E                 return outcome.get_result()
INTERNALERROR> E               File "/nix/store/r4lwmmknxwx3gq2bv73yf0rkli9d902d-python3.8-pluggy-0.13.1/lib/python3.8/site-packages/pluggy/callers.py", line 80, in get_result
INTERNALERROR> E                 raise ex[1].with_traceback(ex[2])
INTERNALERROR> E               File "/nix/store/r4lwmmknxwx3gq2bv73yf0rkli9d902d-python3.8-pluggy-0.13.1/lib/python3.8/site-packages/pluggy/callers.py", line 187, in _multicall
INTERNALERROR> E                 res = hook_impl.function(*args)
INTERNALERROR> E               File "/build/SQLAlchemy-1.4.15/test/../lib/sqlalchemy/testing/plugin/pytestplugin.py", line 135, in pytest_sessionstart
INTERNALERROR> E                 asyncio._assume_async(plugin_base.post_begin)
INTERNALERROR> E               File "/nix/store/03hwa29jf7794x48983j44g0qvancijw-python3.8-SQLAlchemy-1.4.15/lib/python3.8/site-packages/sqlalchemy/testing/asyncio.py", line 50, in _assume_async
INTERNALERROR> E                 return _util_async_run(fn, *args, **kwargs)
INTERNALERROR> E               File "/nix/store/03hwa29jf7794x48983j44g0qvancijw-python3.8-SQLAlchemy-1.4.15/lib/python3.8/site-packages/sqlalchemy/util/_concurrency_py3k.py", line 167, in _util_async_run
INTERNALERROR> E                 loop = asyncio.get_event_loop()
INTERNALERROR> E               File "/nix/store/4s0h5aawbap3xhldxhcijvl26751qrjr-python3-3.8.9/lib/python3.8/asyncio/events.py", line 639, in get_event_loop
INTERNALERROR> E                 raise RuntimeError('There is no current event loop in thread %r.'
INTERNALERROR> E             RuntimeError: There is no current event loop in thread 'Dummy-1'.
INTERNALERROR> E           assert False
INTERNALERROR>
INTERNALERROR> /nix/store/ws9fk09ssyzhy93i8janlh274nay3190-python3.8-pytest-xdist-2.2.1/lib/python3.8/site-packages/xdist/dsession.py:187: AssertionError
[gw18] node down: Not properly terminated

replacing crashed worker gw18
[gw48] linux Python 3.8.9 cwd: /build/SQLAlchemy-1.4.15
gw0 ok / gw1 ok / gw2 ok / gw3 ok / gw4 ok / gw5 ok / gw6 ok / gw7 ok / gw8 ok / gw9 ok / gw10 ok / gw11 ok / gw12 ok / gw13 ok / gw14 ok / gw15 ok / gw16 ok / gw17 ok / gw48 C / gw19 C / gw20 C / gw21 C / gw22 C / gw23 C / gw24 C / gw25 C / gw26 C / gw27 C / gw28 C / gw29 C / gw30 C / gw31 C / gw32 C / gw33 C / gw34 C / gw35 C / gw36 C / gw37 C / gw38 C / gw39 C / gw40 C / gw41 C / gw42 C / gw43 C / gw44 C / gw45 C / gw46 C / gw47 CINTERNALERROR> Traceback (most recent call last):
INTERNALERROR>   File "/nix/store/4v6lhz8sq9jwl3af8abs6cgpbh9lignr-python3.8-pytest-6.2.3/lib/python3.8/site-packages/_pytest/main.py", line 269, in wrap_session
INTERNALERROR>     session.exitstatus = doit(config, session) or 0
INTERNALERROR>   File "/nix/store/4v6lhz8sq9jwl3af8abs6cgpbh9lignr-python3.8-pytest-6.2.3/lib/python3.8/site-packages/_pytest/main.py", line 323, in _main
INTERNALERROR>     config.hook.pytest_runtestloop(session=session)
INTERNALERROR>   File "/nix/store/r4lwmmknxwx3gq2bv73yf0rkli9d902d-python3.8-pluggy-0.13.1/lib/python3.8/site-packages/pluggy/hooks.py", line 286, in __call__
INTERNALERROR>     return self._hookexec(self, self.get_hookimpls(), kwargs)
INTERNALERROR>   File "/nix/store/r4lwmmknxwx3gq2bv73yf0rkli9d902d-python3.8-pluggy-0.13.1/lib/python3.8/site-packages/pluggy/manager.py", line 93, in _hookexec
INTERNALERROR>     return self._inner_hookexec(hook, methods, kwargs)
INTERNALERROR>   File "/nix/store/r4lwmmknxwx3gq2bv73yf0rkli9d902d-python3.8-pluggy-0.13.1/lib/python3.8/site-packages/pluggy/manager.py", line 84, in <lambda>
INTERNALERROR>     self._inner_hookexec = lambda hook, methods, kwargs: hook.multicall(
INTERNALERROR>   File "/nix/store/r4lwmmknxwx3gq2bv73yf0rkli9d902d-python3.8-pluggy-0.13.1/lib/python3.8/site-packages/pluggy/callers.py", line 208, in _multicall
INTERNALERROR>     return outcome.get_result()
INTERNALERROR>   File "/nix/store/r4lwmmknxwx3gq2bv73yf0rkli9d902d-python3.8-pluggy-0.13.1/lib/python3.8/site-packages/pluggy/callers.py", line 80, in get_result
INTERNALERROR>     raise ex[1].with_traceback(ex[2])
INTERNALERROR>   File "/nix/store/r4lwmmknxwx3gq2bv73yf0rkli9d902d-python3.8-pluggy-0.13.1/lib/python3.8/site-packages/pluggy/callers.py", line 187, in _multicall
INTERNALERROR>     res = hook_impl.function(*args)
INTERNALERROR>   File "/nix/store/ws9fk09ssyzhy93i8janlh274nay3190-python3.8-pytest-xdist-2.2.1/lib/python3.8/site-packages/xdist/dsession.py", line 112, in pytest_runtestloop
INTERNALERROR>     self.loop_once()
INTERNALERROR>   File "/nix/store/ws9fk09ssyzhy93i8janlh274nay3190-python3.8-pytest-xdist-2.2.1/lib/python3.8/site-packages/xdist/dsession.py", line 135, in loop_once
INTERNALERROR>     call(**kwargs)
INTERNALERROR>   File "/nix/store/ws9fk09ssyzhy93i8janlh274nay3190-python3.8-pytest-xdist-2.2.1/lib/python3.8/site-packages/xdist/dsession.py", line 224, in worker_errordown
INTERNALERROR>     self._active_nodes.remove(node)
INTERNALERROR> KeyError: <WorkerController gw18>

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

@@ -29,14 +29,9 @@ buildPythonPackage rec {
 
   checkInputs = [
     pytestCheckHook
-    pytest_xdist
     mock
   ] ++ lib.optional (!isPy3k) pysqlite;
 
-  pytestFlagsArray = [
-    "-n auto"
-  ];
-
   postInstall = ''
     sed -e 's:--max-worker-restart=5::g' -i setup.cfg
   '';