* Use test_utils.run_briefly() to execute pending calls to really close
transports
* sslproto: mock also _SSLPipe.shutdown(), it's need to close the transport
* pipe test: the test doesn't close explicitly the PipeHandle, so ignore
the warning instead
* test_popen: use the context manager ("with p:") to explicitly close pipes
Don't call immediatly self._process_write_backlog() but schedule the call using
call_soon(). _on_handshake_complete() can be called indirectly from
_process_write_backlog(), and _process_write_backlog() is not reentrant.
* PipeHandle now uses None instead of -1 for a closed handle
* Sort imports in windows_utils.
* Fix test_events on Python older than 3.5. Skip SSL tests on the
ProactorEventLoop if ssl.MemoryIO is missing
* Fix BaseEventLoop._create_connection_transport(). Close the transport if the
creation of the transport (if the waiter) gets an exception.
* _ProactorBasePipeTransport now sets _sock to None when the transport is
closed.
* Fix BaseSubprocessTransport.close(). Ignore pipes for which the protocol is
not set yet (still equal to None).
* TestLoop.close() now calls the close() method of the parent class
(BaseEventLoop).
* Cleanup BaseSelectorEventLoop: create the protocol on a separated line for
readability and ease debugging.
* Fix BaseSubprocessTransport._kill_wait(). Set the _returncode attribute, so
close() doesn't try to terminate the process.
* Tests: explicitly close event loops and transports
* UNIX pipe transports: add closed/closing in repr(). Add "closed" or "closing"
state in the __repr__() method of _UnixReadPipeTransport and
_UnixWritePipeTransport classes.
"_Atomic void*" types work. Change needed on FreeBSD 10 where stdatomic.h is
available but the compiler fails on "_Atomic void*" with "_Atomic cannot be
applied to incomplete type 'void'".
* If an exception is raised during the creation of a subprocess, kill the
subprocess (close pipes, kill and read the return status). Log an error in
such case.
* Fix SubprocessStreamProtocol.connection_made() to handle cancelled waiter.
Add unit test cancelling subprocess methods.
- Add a new _wakeup_waiter() method
- Replace _create_waiter() method with a _wait_for_data() coroutine function
- Use the value None instead of True or False to wake up the waiter
