add _load_params debug overrides for module args/file passed on cmdline

Updated python module wrapper explode method to drop 'args' file next to module.
Both execute() and excommunicate() debug methods now pass the module args via file to enable debuggers that are picky about stdin.
Updated unit tests to use a context manager for masking/restoring default streams and argv.

test/units/module_utils/basic/test_run_command.py

@@ -25,12 +25,11 @@ import sys
 import time
 from io import BytesIO, StringIO
 
-from ansible.compat.six import PY3
-from ansible.utils.unicode import to_bytes
-
 from ansible.compat.tests import unittest
 from ansible.compat.tests.mock import call, MagicMock, Mock, patch, sentinel
 
+from units.mock.procenv import swap_stdin_and_argv
+
 from ansible.module_utils import basic
 from ansible.module_utils.basic import AnsibleModule
 
@@ -46,9 +45,7 @@ class OpenBytesIO(BytesIO):
 
 @unittest.skipIf(sys.version_info[0] >= 3, "Python 3 is not supported on targets (yet)")
 class TestAnsibleModuleRunCommand(unittest.TestCase):
-
     def setUp(self):
-
         self.cmd_out = {
             # os.read() is returning 'bytes', not strings
             sentinel.stdout: BytesIO(),
@@ -66,11 +63,10 @@ class TestAnsibleModuleRunCommand(unittest.TestCase):
                 raise OSError(errno.EPERM, "Permission denied: '/inaccessible'")
 
         args = json.dumps(dict(ANSIBLE_MODULE_ARGS={}, ANSIBLE_MODULE_CONSTANTS={}))
-        if PY3:
-            sys.stdin = StringIO(args)
-            sys.stdin.buffer = BytesIO(to_bytes(args))
-        else:
-            sys.stdin = BytesIO(to_bytes(args))
+        # unittest doesn't have a clean place to use a context manager, so we have to enter/exit manually
+        self.stdin_swap = swap_stdin_and_argv(stdin_data=args)
+        self.stdin_swap.__enter__()
+
         self.module = AnsibleModule(argument_spec=dict())
         self.module.fail_json = MagicMock(side_effect=SystemExit)
 
@@ -96,6 +92,11 @@ class TestAnsibleModuleRunCommand(unittest.TestCase):
 
         self.addCleanup(patch.stopall)
 
+
+    def tearDown(self):
+        # unittest doesn't have a clean place to use a context manager, so we have to enter/exit manually
+        self.stdin_swap.__exit__(None, None, None)
+
     def test_list_as_args(self):
         self.module.run_command(['/bin/ls', 'a', ' b', 'c '])
         self.assertTrue(self.subprocess.Popen.called)