Restore SIGPIPE handler to DFL on POpen

Python sets the SIGPIPE handler to SIG_IGN. On execv() signal handlers are
reset to their defaults, EXCEPT those that are SIG_IGN which are left ignored.
In Python 3 subprocess.popen explicitly resets the SIGPIPE handler to SIG_DFL,
but unfortunately in Python 2.7 it does not. This leads to subprocesses being
executed with SIGPIPE ignored. This is often a problem with bash scripts which
rely on SIGPIPE to terminate commands in a pipe, but can easily be a problem
with other applications.

This implements the Python 3 behaviour for Python 2.7 by using a preexec_fn.

changelogs/fragments/restore_sigpipe_dfl.yml

@@ -0,0 +1,2 @@
+bugfixes:
+    - Restore SIGPIPE to SIG_DFL when creating subprocesses to avoid it being ignored under Python 2.

lib/ansible/module_utils/basic.py

@@ -68,6 +68,7 @@ import locale
 import os
 import re
 import shlex
+import signal
 import subprocess
 import sys
 import types
@@ -2681,6 +2682,11 @@ class AnsibleModule(object):
 
         return self._clean
 
+    def _restore_signal_handlers(self):
+        # Reset SIGPIPE to SIG_DFL, otherwise in Python2.7 it gets ignored in subprocesses.
+        if PY2 and sys.platform != 'win32':
+            signal.signal(signal.SIGPIPE, signal.SIG_DFL)
+
     def run_command(self, args, check_rc=False, close_fds=True, executable=None, data=None, binary_data=False, path_prefix=None, cwd=None,
                     use_unsafe_shell=False, prompt_regex=None, environ_update=None, umask=None, encoding='utf-8', errors='surrogate_or_strict',
                     expand_user_and_vars=True):
@@ -2825,6 +2831,7 @@ class AnsibleModule(object):
             stdin=st_in,
             stdout=subprocess.PIPE,
             stderr=subprocess.PIPE,
+            preexec_fn=self._restore_signal_handlers,
         )
 
         # store the pwd