Hack to work around callback API change for v2_playbook_on_start

lib/ansible/executor/task_queue_manager.py

@@ -288,7 +288,20 @@ class TaskQueueManager:
             for method in methods:
                 if method is not None:
                     try:
-                        method(*args, **kwargs)
+                        # temporary hack, required due to a change in the callback API, so
+                        # we don't break backwards compatibility with callbacks which were
+                        # designed to use the original API
+                        # FIXME: target for removal and revert to the original code here
+                        #        after a year (2017-01-14)
+                        if method_name == 'v2_playbook_on_start':
+                            import inspect
+                            (f_args, f_varargs, f_keywords, f_defaults) = inspect.getargspec(method)
+                            if 'playbook' in args:
+                                method(*args, **kwargs)
+                            else:
+                                method()
+                        else:
+                            method(*args, **kwargs)
                     except Exception as e:
                         import traceback
                         orig_tb = traceback.format_exc()