Using pchroot in pytest script fails

[BrendanSimon]

The following script run with pytest fails with:

E               io.UnsupportedOperation: redirected stdin is pseudofile, has no fileno()

---

from pychroot import Chroot
import os

chroot_path = '/tmp/foo/bar'

os.makedirs( chroot_path, exist_ok=True)

def test_chroot () :
    with Chroot( chroot_path ) :
        answer = 42
        print( answer )

---

Output:

$ pytest chroot_test.py 
========================== test session starts ===========================
platform linux -- Python 3.6.7, pytest-5.3.2, py-1.8.1, pluggy-0.13.1
rootdir: /tmp
collected 1 item                                                         

chroot_test.py F                                                   [100%]

================================ FAILURES ================================
______________________________ test_chroot _______________________________

    def test_chroot () :
        with Chroot( chroot_path ) :
>           answer = 42

chroot_test.py:10: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

    def test_chroot () :
        with Chroot( chroot_path ) :
>           answer = 42

chroot_test.py:10: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <pychroot.base.Chroot object at 0x7fe1ec9d0ef0>
frame = <frame object at 0x7fe1eb906048>, event = 'line', arg = None

    def __invoke_trace_funcs(self, frame, event, arg):
        """Invoke all trace funcs that have been injected.

        Once the injected functions have been executed all trace hooks are
        removed in order to minimize overhead.
        """
        try:
            for func in self.__injected_trace_funcs[frame]:
>               func(frame, event, arg)

/home/brendan/SEPL/brickstrap/brickstrap/ind-efd/venv_3.6.7/lib/python3.6/site-packages/snakeoil/contexts.py:237: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <pychroot.base.Chroot object at 0x7fe1ec9d0ef0>
frame = <frame object at 0x7fe1eb906048>, event = 'line', arg = None

    def __exit_context(self, frame, event, arg):
        """Simple function to throw a ParentException."""
>       raise self.ParentException()
E       snakeoil.contexts.SplitExec.ParentException

/home/brendan/SEPL/brickstrap/brickstrap/ind-efd/venv_3.6.7/lib/python3.6/site-packages/snakeoil/contexts.py:212: ParentException

During handling of the above exception, another exception occurred:

    def test_chroot () :
        with Chroot( chroot_path ) :
            answer = 42
>           print(answer)

chroot_test.py:11: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <pychroot.base.Chroot object at 0x7fe1ec9d0ef0>
exc_type = <class 'snakeoil.contexts.SplitExec.ParentException'>
exc_value = ParentException()
exc_traceback = <traceback object at 0x7fe1eb8f3308>

    def __exit__(self, exc_type, exc_value, exc_traceback):
        if self.childpid is not None:
            # make sure system tracing function is reset
            self.__revert_tracing(inspect.currentframe())
            # re-raise unknown exceptions from the parent
            if exc_type is not self.ParentException:
                raise exc_value

            # get exception from the child
            try:
                exc = self.__pipe.recv()
                self.locals = exc._locals
            except EOFError as e:
                exc = SystemExit(e)

            # handle child exiting abnormally
            if not isinstance(exc, SystemExit):
                os.waitpid(self.childpid, 0)
                self._exception_cleanup()
                sys.excepthook = self.__excepthook
>               raise exc
E               io.UnsupportedOperation: redirected stdin is pseudofile, has no fileno()

/home/brendan/SEPL/brickstrap/brickstrap/ind-efd/venv_3.6.7/lib/python3.6/site-packages/snakeoil/contexts.py:163: UnsupportedOperation
=========================== 1 failed in 0.11s ============================
(venv_3.6.7) brendan@osboxes:/tmp$ 

[radhermit]

pychroot often doesn't handle running within pytest's modified testing environment at this point without mocking out various aspects. In this case you'd need to run the tests with pytest's stdin/stdout capturing disabled (use the -s argument for pytest).

Patches accepted if you can figure out how to improve the situation, but I don't want to insert hacks into the codebase to work around specific test platform quirks.