asyncio: sync with Tulip

* Fix pyflakes warnings: remove unused imports and variables
* asyncio.test_support now uses test.support and test.script_helper if available

Lib/test/test_asyncio/test_base_events.py

@@ -14,8 +14,8 @@ from asyncio import base_events
 from asyncio import constants
 from asyncio import test_utils
 try:
-    from test.script_helper import assert_python_ok
     from test import support
+    from test.script_helper import assert_python_ok
 except ImportError:
     from asyncio import test_support as support
     from asyncio.test_support import assert_python_ok

Lib/test/test_asyncio/test_events.py

@@ -27,7 +27,7 @@ from asyncio import proactor_events
 from asyncio import selector_events
 from asyncio import test_utils
 try:
-    from test import support  # find_unused_port, IPV6_ENABLED, TEST_HOME_DIR
+    from test import support
 except ImportError:
     from asyncio import test_support as support
 

Lib/test/test_asyncio/test_futures.py

@@ -10,7 +10,7 @@ from unittest import mock
 import asyncio
 from asyncio import test_utils
 try:
-    from test import support   # gc_collect
+    from test import support
 except ImportError:
     from asyncio import test_support as support
 

Lib/test/test_asyncio/test_selector_events.py

 """Tests for selector_events.py"""
 
 import errno
-import gc
-import pprint
 import socket
-import sys
 import unittest
 from unittest import mock
 try:

Lib/test/test_asyncio/test_subprocess.py

@@ -6,12 +6,12 @@ from unittest import mock
 import asyncio
 from asyncio import subprocess
 from asyncio import test_utils
-if sys.platform != 'win32':
-    from asyncio import unix_events
 try:
-    from test import support   # PIPE_MAX_SIZE
+    from test import support
 except ImportError:
     from asyncio import test_support as support
+if sys.platform != 'win32':
+    from asyncio import unix_events
 
 # Program blocking
 PROGRAM_BLOCKED = [sys.executable, '-c', 'import time; time.sleep(3600)']

Lib/test/test_asyncio/test_tasks.py

@@ -7,17 +7,17 @@ import types
 import unittest
 import weakref
 from unittest import mock
+
+import asyncio
+from asyncio import coroutines
+from asyncio import test_utils
 try:
-    from test import support   # gc_collect
+    from test import support
     from test.script_helper import assert_python_ok
 except ImportError:
     from asyncio import test_support as support
     from asyncio.test_support import assert_python_ok
 
-import asyncio
-from asyncio import coroutines
-from asyncio import test_utils
-
 
 PY34 = (sys.version_info >= (3, 4))
 PY35 = (sys.version_info >= (3, 5))

Lib/test/test_asyncio/test_unix_events.py

 """Tests for unix_events.py."""
 
 import collections
-import gc
 import errno
 import io
 import os
-import pprint
 import signal
 import socket
 import stat

Lib/test/test_asyncio/test_windows_utils.py

@@ -5,18 +5,17 @@ import sys
 import unittest
 from unittest import mock
 
-try:
-    from test import support  # gc_collect, IPV6_ENABLED
-except ImportError:
-    from asyncio import test_support as support
-
 if sys.platform != 'win32':
     raise unittest.SkipTest('Windows only')
 
 import _winapi
 
-from asyncio import windows_utils
 from asyncio import _overlapped
+from asyncio import windows_utils
+try:
+    from test import support
+except ImportError:
+    from asyncio import test_support as support
 
 
 class WinsocketpairTests(unittest.TestCase):