asyncio: sync with Tulip

* Tulip issue #182: Improve logs of BaseEventLoop._run_once()

  - Don't log non-blocking poll
  - Only log polling with a timeout if it gets events or if it timed out after
    more than 1 second.

* Fix some pyflakes warnings: remove unused imports

Lib/test/test_asyncio/test_base_events.py

@@ -12,7 +12,6 @@ from test.support import IPV6_ENABLED
 
 import asyncio
 from asyncio import base_events
-from asyncio import events
 from asyncio import constants
 from asyncio import test_utils
 
@@ -26,6 +25,7 @@ class BaseEventLoopTests(test_utils.TestCase):
     def setUp(self):
         self.loop = base_events.BaseEventLoop()
         self.loop._selector = mock.Mock()
+        self.loop._selector.select.return_value = ()
         self.set_event_loop(self.loop)
 
     def test_not_implemented(self):

Lib/test/test_asyncio/test_events.py

@@ -715,7 +715,7 @@ class EventLoopTestsMixin:
             with self.assertRaisesRegex(ValueError,
                                         'path and sock can not be specified '
                                         'at the same time'):
-                server = self.loop.run_until_complete(f)
+                self.loop.run_until_complete(f)
 
     def _create_ssl_context(self, certfile, keyfile=None):
         sslcontext = ssl.SSLContext(ssl.PROTOCOL_SSLv23)

Lib/test/test_asyncio/test_tasks.py

@@ -1,6 +1,5 @@
 """Tests for tasks.py."""
 
-import os.path
 import re
 import sys
 import types
@@ -1640,9 +1639,9 @@ class TaskTests(test_utils.TestCase):
             asyncio.coroutines._DEBUG = debug
 
         tb_filename = __file__
-        tb_lineno = sys._getframe().f_lineno + 1
-        coro = coro_noop()
-        coro = None
+        tb_lineno = sys._getframe().f_lineno + 2
+        # create a coroutine object but don't use it
+        coro_noop()
         support.gc_collect()
 
         self.assertTrue(m_log.error.called)
@@ -1652,7 +1651,7 @@ class TaskTests(test_utils.TestCase):
                  r'Coroutine object created at \(most recent call last\):\n'
                  r'.*\n'
                  r'  File "%s", line %s, in test_coroutine_never_yielded\n'
-                 r'    coro = coro_noop\(\)$'
+                 r'    coro_noop\(\)$'
                  % (re.escape(coro_noop.__qualname__),
                     re.escape(func_filename), func_lineno,
                     re.escape(tb_filename), tb_lineno))