Add better error when k=v syntax is used with YAML in tasks (#41754)

* Add error message for k=v and YAML in a single task

Find the correct line, column, and position for k=v errors since they are different than the position reported initially.

Document bug in quoting syntax check.

* Change tense or error message

Since the error still exists, switch to present tense rather than past tense.

* Remove double spaces after periods in error messages.

http://www.slate.com/articles/technology/technology/2011/01/space_invaders.html

* Add changelog fragment

* Add tests for new error message

* Fix tests

* Add clarifying comments to unit test

test/units/playbook/test_task.py

@@ -84,11 +84,11 @@ class TestTask(unittest.TestCase):
         self.assertIsInstance(cm.exception, errors.AnsibleParserError)
         self.assertEqual(cm.exception._obj, ds)
         self.assertEqual(cm.exception._obj, kv_bad_args_ds)
-        self.assertIn("The error appears to have been in 'test_task_faux_playbook.yml", cm.exception.message)
+        self.assertIn("The error appears to be in 'test_task_faux_playbook.yml", cm.exception.message)
         self.assertIn(kv_bad_args_str, cm.exception.message)
         self.assertIn('apk', cm.exception.message)
         self.assertEquals(cm.exception.message.count('The offending line'), 1)
-        self.assertEquals(cm.exception.message.count('The error appears to have been in'), 1)
+        self.assertEquals(cm.exception.message.count('The error appears to be in'), 1)
 
     def test_task_auto_name(self):
         assert 'name' not in kv_command_task