Update pexpect to 4.6.0

[pyup-bot]

This PR updates pexpect from 4.3.1 to 4.6.0.

Changelog

4.6

* The :meth:`.pxssh.login` method now supports an ``ssh_config`` parameter,
which can be used to specify a file path to an SSH config file
(:ghpull:`490`).
* Improved compatability for the ``crlf`` parameter of :class:`~.PopenSpawn`
(:ghpull:`493`)
* Fixed an issue in read timeout handling when using :class:`~.spawn` and
:class:`~.fdspawn` with the ``use_poll`` parameter (:ghpull:`492`).

4.5

* :class:`~.spawn` and :class:`~.fdspawn` now have a ``use_poll`` parameter.
If this is True, they will use :func:`select.poll` instead of :func:`select.select`.
``poll()`` allows file descriptors above 1024, but it must be explicitly
enabled due to compatibility concerns (:ghpull:`474`).
* The :meth:`.pxssh.login` method has several new and changed options:

* The option ``password_regex`` allows changing
 the password prompt regex, for servers that include ``password:`` in a banner
 before reaching a prompt (:ghpull:`468`).
* :meth:`~.pxssh.login` now allows for setting up SSH tunnels to be requested once
 logged in to the remote server. This option is ``ssh_tunnels`` (:ghpull:`473`).
 The structure should be like this::

       {
         'local': ['2424:localhost:22'],    Local SSH tunnels
         'remote': ['2525:localhost:22'],   Remote SSH tunnels
         'dynamic': [8888],                 Dynamic/SOCKS tunnels
       }

* The option ``spawn_local_ssh=False`` allows subsequent logins from the
 remote session and treats the session as if it was local (:ghpull:`472`).
* Setting ``sync_original_prompt=False`` will prevent changing the prompt to
 something unique, in case the remote server is sensitive to new lines at login
 (:ghpull:`468`).
* If ``ssh_key=True`` is passed, the SSH client forces forwarding the authentication
 agent to the remote server instead of providing a key (:ghpull:`473`).

4.4

* :class:`~.PopenSpawn` now has a ``preexec_fn`` parameter, like :class:`~.spawn`
and :class:`subprocess.Popen`, for a function to be called in the child
process before executing the new command. Like in ``Popen``, this works only
in POSIX, and can cause issues if your application also uses threads
(:ghpull:`460`).
* Significant performance improvements when processing large amounts of data
(:ghpull:`464`).
* Ensure that ``spawn.closed`` gets set by :meth:`~.spawn.close`, and improve
an example for passing ``SIGWINCH`` through to a child process (:ghpull:`466`).

Links

• PyPI: https://pypi.org/project/pexpect
• Changelog: https://pyup.io/changelogs/pexpect/
• Docs: https://pexpect.readthedocs.io/