dereference aliased tornado methods/classes

 * Tornado v5.0.0 made some old methods/classes aliases for other
   entities.  Per their release notes[1], replace the aliases with
   direct calls to the aliasee:

   * Replace tornado.ioloop.IOLoop.instance() with
     asyncio.get_event_loop(). instance() is an alias to .current(),
     which (for WB's usage) is an alias to get_event_loop().

   * Replace tornado.concurrent.Future with asyncio.Future

 [1] https://github.com/tornadoweb/tornado/blob/master/docs/releases/v5.0.0.rst

Author: felliott

tests/utils.py

@@ -7,7 +7,7 @@
 from unittest import mock
 
 import pytest
-from tornado import concurrent, testing
+from tornado import testing
 from tornado.platform.asyncio import AsyncIOMainLoop
 
 from waterbutler.server.app import make_app
@@ -75,7 +75,7 @@ def __init__(self):
         super().__init__(tempfile.TemporaryFile())
 
 
-class MockRequestBody(concurrent.Future):
+class MockRequestBody(asyncio.Future):
 
     def __await__(self):
         yield None

waterbutler/server/app.py

@@ -19,7 +19,7 @@
 
 
 def sig_handler(sig, frame):
-    io_loop = tornado.ioloop.IOLoop.instance()
+    io_loop = asyncio.get_event_loop()
 
     def stop_loop():
         if len(asyncio.Task.all_tasks(io_loop)) == 0:
@@ -43,7 +43,7 @@ def make_app(debug):
         api_to_handlers(v1) +
         [(r'/status', handlers.StatusHandler)],
         debug=debug,
-        autoreload=False
+        autoreload=False,
     )
     app.sentry_client = AsyncSentryClient(settings.SENTRY_DSN, release=__version__)
     return app