Add some more unittests for fail_json

Test that order of msg as a keyword arg doesn't matter

test/units/module_utils/basic/test_exit_json.py

@@ -7,6 +7,7 @@ from __future__ import (absolute_import, division)
 __metaclass__ = type
 
 import json
+import sys
 
 import pytest
 
@@ -67,11 +68,31 @@ class TestAnsibleModuleExitJson:
         assert return_val == {'msg': 'This is the msg', 'failed': True,
                               'invocation': EMPTY_INVOCATION}
 
+    @pytest.mark.parametrize('stdin', [{}], indirect=['stdin'])
+    def test_fail_json_msg_as_kwarg_after(self, am, capfd):
+        """Test that msg as a kwarg after other kwargs works"""
+        with pytest.raises(SystemExit) as ctx:
+            am.fail_json(arbitrary=42, msg='This is the msg')
+        assert ctx.value.code == 1
+
+        out, err = capfd.readouterr()
+        return_val = json.loads(out)
+        # Fail_json should add failed=True
+        assert return_val == {'msg': 'This is the msg', 'failed': True,
+                              'arbitrary': 42,
+                              'invocation': EMPTY_INVOCATION}
+
     @pytest.mark.parametrize('stdin', [{}], indirect=['stdin'])
     def test_fail_json_no_msg(self, am):
         with pytest.raises(TypeError) as ctx:
             am.fail_json()
-        assert ctx.value.args[0] == "fail_json() missing 1 required positional argument: 'msg'"
+
+        if sys.version_info < (3,):
+            error_msg = "fail_json() takes exactly 2 arguments (1 given)"
+        else:
+            error_msg = "fail_json() missing 1 required positional argument: 'msg'"
+
+        assert ctx.value.args[0] == error_msg
 
 
 class TestAnsibleModuleExitValuesRemoved: