Deprecation notice for sprockets.http.run.

sprockets.http.run will only accept sprockets.app.Application instances
in the near future.  I'm doing this so that we can clean up the runner
code significantly as we move to using `async` and `await` instead of
futures.

docs/history.rst

@@ -3,10 +3,12 @@
 Release History
 ===============
 
-Next release
-------------
+`Next release`_
+---------------
 - Updated to support Python 3.9.  ``asyncio.Task.all_tasks`` was removed
   so I switched to ``asyncio.all_tasks`` if it exists.
+- Deprecate calling ``sprockets.http.run`` with anything that isn't a
+  ``sprockets.app.Application`` instance.
 
 `2.1.1`_ (19 Feb 2020)
 ----------------------

sprockets/http/app.py

@@ -1,6 +1,7 @@
 import asyncio
 import logging
 import sys
+import warnings
 
 from tornado import concurrent, web
 
@@ -260,6 +261,11 @@ def wrap_application(application, before_run, on_start, shutdown):
     shutdown = [] if shutdown is None else shutdown
 
     if not isinstance(application, Application):
+        warnings.warn(
+            'sprockets.http.run is only going to accept '
+            'sprockets.app.Application instances in 3.0, '
+            'was called with {}'.format(type(application).__name__),
+            category=DeprecationWarning)
         application = _ApplicationAdapter(application)
 
     application.before_run_callbacks.extend(before_run)

tests.py

@@ -469,6 +469,21 @@ class RunnerTests(MockHelper, unittest.TestCase):
         self.io_loop.stop.assert_called_once_with()
         self.assertNotEqual(self.io_loop._timeouts, [])
 
+    def test_that_calling_with_non_sprockets_application_is_deprecated(self):
+        with warnings.catch_warnings(record=True) as captured:
+            warnings.filterwarnings(action='always', module='sprockets')
+            sprockets.http.runner.Runner(web.Application())
+        for warning in captured:
+            if 'sprockets.app.Application' in str(warning.message):
+                break
+        else:
+            self.fail('expected deprecation warning from runnr.Runner')
+
+        with warnings.catch_warnings(record=True) as captured:
+            warnings.filterwarnings(action='always', module='sprockets')
+            sprockets.http.runner.Runner(sprockets.http.app.Application())
+        self.assertEqual(len(captured), 0)
+
 
 class AsyncRunTests(unittest.TestCase):