Fix the subprocess leak issue in the nox/popen.py file

[wu-zhao-min]

Problem description : The popen() function in nox/popen.py creates a child process with subprocess.Popen() and calls proc.communicate() inside a try block whose only except clause catches KeyboardInterrupt . On any other exception path (e.g. OSError from a broken pipe, subprocess.SubprocessError , or a disk-full error while writing to a redirected stdout file), the exception propagates without terminating or waiting on the child. Neither proc.terminate() / proc.kill() nor proc.wait() is invoked, and the Popen object's stdin / stdout / stderr pipe file descriptors are released only by non-deterministic garbage collection rather than deterministically.

Hazard statement : During stress testing, every session.run() invocation that hits a transient I/O error during communicate() leaks one orphaned child process (which keeps running and consuming memory/CPU) together with its pipe file descriptors. Long-term stress testing accumulates orphan processes and exhausts file descriptors, eventually causing "too many open files" errors or system resource exhaustion.

Repair solution : Wrap the subprocess.Popen() call in a with statement so that Popen.exit waits for the process and closes its pipes, and add a finally block that calls proc.kill() whenever proc.poll() is None , ensuring the child is terminated and reaped on every exit path—including non- KeyboardInterrupt exceptions.

[wu-zhao-min]

closed