Hi,
We use the sh module in a threaded context to execute shell commands. When we were migrating to python 3 from python 2 we encountered some commands hanging. We created a test script that recreates the issue we are seeing.
`import sh
import logging
import concurrent.futures.thread

def execmd(exe):
print(sh.ls())
execution_pool = concurrent.futures.thread.ThreadPoolExecutor(20)
i = 0
thread_results = []
while i<500:
i+= 1
thread_results.append(execution_pool.map(execmd, ['ls']))

execution_pool.shutdown()

When running this in python 3.7 it hangs but in python 3.6 it works fine. We think it is releated to this issue https://bugs.python.org/issue36533. Installing the latest 3.7.4 didn't fix the issue.  The sh module uses logging and forking and the top script uses threading so we think there is a locking issue with 3.7.  Any help would be great.

os.fork() cannot be safely used in an application that uses threads in any manner.  This is not something Python can fix.  This is a POSIX limitation.

The "sh" module on PyPI is incompatible with threaded applications on POSIX platforms due to its use of os.fork().

https://github.com/amoffat/sh/blob/master/sh.py#L1861

Raise this issue with them.