* Add a new asyncio.subprocess module
* Add new create_subprocess_exec() and create_subprocess_shell() functions
* The new asyncio.subprocess.SubprocessStreamProtocol creates stream readers
for stdout and stderr and a stream writer for stdin.
* The new asyncio.subprocess.Process class offers an API close to the
subprocess.Popen class:
- pid, returncode, stdin, stdout and stderr attributes
- communicate(), wait(), send_signal(), terminate() and kill() methods
* Remove STDIN (0), STDOUT (1) and STDERR (2) constants from base_subprocess
and unix_events, to not be confused with the symbols with the same name of
subprocess and asyncio.subprocess modules
* _ProactorBasePipeTransport.get_write_buffer_size() now counts also the size
of the pending write
* _ProactorBaseWritePipeTransport._loop_writing() may now pause the protocol if
the write buffer size is greater than the high water mark (64 KB by default)
Victor Stinner
Guido van Rossum
Andrew Svetlov
Guido van Rossum