arbiter: don't log messages when handling SIGCHLD

Fixes benoitc#2816

Logging stuff in a signal handler cannot work and thus must not be done.
https://docs.python.org/3/library/logging.html#thread-safety

gunicorn/arbiter.py

@@ -532,27 +532,6 @@ def reap_workers(self):
                         reason = "App failed to load."
                         raise HaltServer(reason, self.APP_LOAD_ERROR)
 
-                    if exitcode > 0:
-                        # If the exit code of the worker is greater than 0,
-                        # let the user know.
-                        self.log.error("Worker (pid:%s) exited with code %s.",
-                                       wpid, exitcode)
-                    elif status > 0:
-                        # If the exit code of the worker is 0 and the status
-                        # is greater than 0, then it was most likely killed
-                        # via a signal.
-                        try:
-                            sig_name = signal.Signals(status).name
-                        except ValueError:
-                            sig_name = "code {}".format(status)
-                        msg = "Worker (pid:{}) was sent {}!".format(
-                            wpid, sig_name)
-
-                        # Additional hint for SIGKILL
-                        if status == signal.SIGKILL:
-                            msg += " Perhaps out of memory?"
-                        self.log.error(msg)
-
                     worker = self.WORKERS.pop(wpid, None)
                     if not worker:
                         continue