Remove unused imports. (python#435)

Author: JustinTArthur

asyncio/base_subprocess.py

@@ -3,7 +3,6 @@
 import warnings
 
 from . import compat
-from . import futures
 from . import protocols
 from . import transports
 from .coroutines import coroutine

asyncio/queues.py

@@ -7,7 +7,6 @@
 
 from . import compat
 from . import events
-from . import futures
 from . import locks
 from .coroutines import coroutine
 

release.py

@@ -20,7 +20,6 @@
 import subprocess
 import sys
 import tempfile
-import textwrap
 
 PROJECT = 'asyncio'
 DEBUG_ENV_VAR = 'PYTHONASYNCIODEBUG'