Commit 3614927

Base class for transports.

Close the transport. If the transport has a buffer for outgoing

data, buffered data will be flushed asynchronously. No more data

will be received. After all buffered data is flushed, the

protocol's :meth:`connection_lost` method will be called with

:const:`None` as its argument.

Return ``True`` if the transport is closing or is closed.

if it hasn't returned, similarly to the

:attr:`subprocess.Popen.returncode` attribute.

Kill the subprocess, as in :meth:`subprocess.Popen.kill`.