patch gen.maybe_future for compatibility with tornado 6

tornado gen.maybe_future is deprecated in >= 5.0 and doesn't accept asyncio coroutine objects or awaitables in general
causing failures with tornado 6 on asyncio

monkeypatch gen.maybe_future for easier backport to 5.x

later, we can update to use our maybe_future throughout

Author: minrk

jupyter_server/utils.py

@@ -395,6 +395,10 @@ def _check_pid_posix(pid):
 
 def maybe_future(obj):
     """Like tornado's gen.maybe_future
+<<<<<<< HEAD:jupyter_server/utils.py
+=======
+
+>>>>>>> dcee71015... patch gen.maybe_future for compatibility with tornado 6:notebook/utils.py
     but more compatible with asyncio for recent versions
     of tornado
     """
@@ -420,3 +424,7 @@ def maybe_future(obj):
 else:
     import tornado.gen
     tornado.gen.maybe_future = maybe_future
+<<<<<<< HEAD:jupyter_server/utils.py
+=======
+
+>>>>>>> dcee71015... patch gen.maybe_future for compatibility with tornado 6:notebook/utils.py