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.

lib/ansible/module_utils/basic.py

@@ -1435,11 +1435,23 @@ class AnsibleModule(object):
 
     def _load_params(self):
         ''' read the input and set the params attribute.  Sets the constants as well.'''
+        # debug overrides to read args from file or cmdline
+
         # Avoid tracebacks when locale is non-utf8
-        if sys.version_info < (3,):
-            buffer = sys.stdin.read()
+        if len(sys.argv) > 1:
+            if os.path.isfile(sys.argv[1]):
+                fd = open(sys.argv[1], 'rb')
+                buffer = fd.read()
+                fd.close()
+            else:
+                buffer = sys.argv[1]
+        # default case, read from stdin
         else:
-            buffer = sys.stdin.buffer.read()
+            if sys.version_info < (3,):
+                buffer = sys.stdin.read()
+            else:
+                buffer = sys.stdin.buffer.read()
+
         try:
             params = json.loads(buffer.decode('utf-8'))
         except ValueError: