OSError: Bad file descriptor raised when using Python 3.4 and USR2 signal

[prestontimmons]

After upgrading a Python 2 application to Python 3.4, I noticed an OSError is raised when sending a USR2 signal to the process. I believe the problem is related to a change in socket behavior in Python 3.4:

https://docs.python.org/3.4/library/os.html#fd-inheritance

I don't know if this is a correct fix, but adding the below lines to Arbiter.start made the OSError go away:

for sock in self.LISTENERS:
    sock.set_inheritable(True)

This is using version 19.2.1.

[berkerpeksag]

The fix LGTM. We probably will need to add a helper function in gunicorn/_compat.py.

[tilgovi]

LGTM