Log Message:
py-asyncssh: updated to 1.13.3

1.13.3:
Added support for setting the Unicode error handling strategy in conjunction \ 
with setting an encoding when creating new SSH sessions, streams, and processes. \ 
This strategy can also be set when specifying a session encoding in \ 
create_server(), and when providing an encoding in the get_comment() and \ 
set_comment() functions on private/public keys and certificates.
Changed handling of Unicode in channels to use incrmeental codec, similar to \ 
what was previously done in process redirection.
Added Python 3.7 to the list of classifiers in setup.py, now that it has been \ 
released.
Updated Travis CI configuration to add Python 3.7 builds, and moved Linux builds \ 
on never versions of Python up to xenial.
Added missing coroutine decorator in test_channel.