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_exit_json.py

@@ -23,39 +23,34 @@ __metaclass__ = type
 import copy
 import json
 import sys
-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 units.mock.procenv import swap_stdin_and_argv, swap_stdout
 
 from ansible.module_utils import basic
 from ansible.module_utils.basic import heuristic_log_sanitize
 from ansible.module_utils.basic import return_values, remove_values
 
+
 empty_invocation = {u'module_args': {}}
 
 @unittest.skipIf(sys.version_info[0] >= 3, "Python 3 is not supported on targets (yet)")
 class TestAnsibleModuleExitJson(unittest.TestCase):
-
     def setUp(self):
-        self.old_stdin = sys.stdin
         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))
+        self.stdin_swap_ctx = swap_stdin_and_argv(stdin_data=args)
+        self.stdin_swap_ctx.__enter__()
 
-        self.old_stdout = sys.stdout
-        self.fake_stream = BytesIO()
-        sys.stdout = self.fake_stream
+        # since we can't use context managers and "with" without overriding run(), call them directly
+        self.stdout_swap_ctx = swap_stdout()
+        self.fake_stream = self.stdout_swap_ctx.__enter__()
 
         self.module = basic.AnsibleModule(argument_spec=dict())
 
     def tearDown(self):
-        sys.stdout = self.old_stdout
-        sys.stdin = self.old_stdin
+        # since we can't use context managers and "with" without overriding run(), call them directly to clean up
+        self.stdin_swap_ctx.__exit__(None, None, None)
+        self.stdout_swap_ctx.__exit__(None, None, None)
 
     def test_exit_json_no_args_exits(self):
         with self.assertRaises(SystemExit) as ctx:
@@ -123,42 +118,24 @@ class TestAnsibleModuleExitValuesRemoved(unittest.TestCase):
                 ),
             )
 
-    def setUp(self):
-        self.old_stdin = sys.stdin
-        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))
-
-        self.old_stdout = sys.stdout
-
-    def tearDown(self):
-        sys.stdin = self.old_stdin
-        sys.stdout = self.old_stdout
-
     def test_exit_json_removes_values(self):
         self.maxDiff = None
         for args, return_val, expected in self.dataset:
-            sys.stdout = BytesIO()
             params = dict(ANSIBLE_MODULE_ARGS=args, ANSIBLE_MODULE_CONSTANTS={})
             params = json.dumps(params)
-            if PY3:
-                sys.stdin = StringIO(params)
-                sys.stdin.buffer = BytesIO(to_bytes(params))
-            else:
-                sys.stdin = BytesIO(to_bytes(params))
-            module = basic.AnsibleModule(
-                argument_spec = dict(
-                    username=dict(),
-                    password=dict(no_log=True),
-                    token=dict(no_log=True),
-                    ),
-                )
-            with self.assertRaises(SystemExit) as ctx:
-                self.assertEquals(module.exit_json(**return_val), expected)
-            self.assertEquals(json.loads(sys.stdout.getvalue()), expected)
+
+            with swap_stdin_and_argv(stdin_data=params):
+                with swap_stdout():
+                    module = basic.AnsibleModule(
+                        argument_spec = dict(
+                            username=dict(),
+                            password=dict(no_log=True),
+                            token=dict(no_log=True),
+                            ),
+                        )
+                    with self.assertRaises(SystemExit) as ctx:
+                        self.assertEquals(module.exit_json(**return_val), expected)
+                    self.assertEquals(json.loads(sys.stdout.getvalue()), expected)
 
     def test_fail_json_removes_values(self):
         self.maxDiff = None
@@ -166,21 +143,17 @@ class TestAnsibleModuleExitValuesRemoved(unittest.TestCase):
             expected = copy.deepcopy(expected)
             del expected['changed']
             expected['failed'] = True
-            sys.stdout = BytesIO()
             params = dict(ANSIBLE_MODULE_ARGS=args, ANSIBLE_MODULE_CONSTANTS={})
             params = json.dumps(params)
-            if PY3:
-                sys.stdin = StringIO(params)
-                sys.stdin.buffer = BytesIO(to_bytes(params))
-            else:
-                sys.stdin = BytesIO(to_bytes(params))
-            module = basic.AnsibleModule(
-                argument_spec = dict(
-                    username=dict(),
-                    password=dict(no_log=True),
-                    token=dict(no_log=True),
-                    ),
-                )
-            with self.assertRaises(SystemExit) as ctx:
-                self.assertEquals(module.fail_json(**return_val), expected)
-            self.assertEquals(json.loads(sys.stdout.getvalue()), expected)
+            with swap_stdin_and_argv(stdin_data=params):
+                with swap_stdout():
+                    module = basic.AnsibleModule(
+                        argument_spec = dict(
+                            username=dict(),
+                            password=dict(no_log=True),
+                            token=dict(no_log=True),
+                            ),
+                        )
+                    with self.assertRaises(SystemExit) as ctx:
+                        self.assertEquals(module.fail_json(**return_val), expected)
+                    self.assertEquals(json.loads(sys.stdout.getvalue()), expected)