Try to fix some of current failures. See error found in CI below. Hopefully this fixes it. There are manycomplexity, we need to make sure the loop has no task after each tests, so we need to close and restore the subprocess watcher. We make it a context manager and provide a decorator. ====================================================================== ERROR: IPython.core.tests.test_magic.test_script_out ---------------------------------------------------------------------- Traceback (most recent call last): File "/opt/hostedtoolcache/Python/3.7.12/x64/lib/python3.7/site-packages/nose/case.py", line 198, in runTest self.test(*self.arg) File "/home/runner/work/ipython/ipython/IPython/testing/decorators.py", line 223, in skipper_func return f(*args, **kwargs) File "/home/runner/work/ipython/ipython/IPython/core/tests/test_magic.py", line 953, in test_script_out ip.run_cell_magic("script", "--out output sh", "echo 'hi'") File "/home/runner/work/ipython/ipython/IPython/core/interactiveshell.py", line 2417, in run_cell_magic result = fn(*args, **kwargs) File "/opt/hostedtoolcache/Python/3.7.12/x64/lib/python3.7/site-packages/decorator.py", line 232, in fun return caller(func, *(extras + args), **kw) File "/home/runner/work/ipython/ipython/IPython/core/magic.py", line 187, in <lambda> call = lambda f, *a, **k: f(*a, **k) File "/home/runner/work/ipython/ipython/IPython/core/magics/script.py", line 216, in shebang stdin=asyncio.subprocess.PIPE, File "/opt/hostedtoolcache/Python/3.7.12/x64/lib/python3.7/asyncio/base_events.py", line 587, in run_until_complete return future.result() File "/opt/hostedtoolcache/Python/3.7.12/x64/lib/python3.7/asyncio/subprocess.py", line 217, in create_subprocess_exec stderr=stderr, **kwds) File "/opt/hostedtoolcache/Python/3.7.12/x64/lib/python3.7/asyncio/base_events.py", line 1544, in subprocess_exec bufsize, **kwargs) File "/opt/hostedtoolcache/Python/3.7.12/x64/lib/python3.7/asyncio/unix_events.py", line 193, in _make_subprocess_transport self._child_watcher_callback, transp) File "/opt/hostedtoolcache/Python/3.7.12/x64/lib/python3.7/asyncio/unix_events.py", line 941, in add_child_handler "Cannot add child handler, " RuntimeError: Cannot add child handler, the child watcher does not have a loop attached