Update pexpect to 4.4.0

[pyup-bot]

There's a new version of pexpect available.
You are currently using 4.2.1. I have updated it to 4.4.0

These links might come in handy: PyPI | Changelog | Docs

Changelog

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).

4.3.1

• When launching bash for :mod:pexpect.replwrap, load the system bashrc
  from a couple of different common locations (:ghpull:457), and then unset
  the PROMPT_COMMAND environment variable, which can interfere with the
  prompt we're expecting (:ghpull:459).

4.3

• The async= parameter to integrate with asyncio has become async_=
  (:ghpull:431), as async is becoming a Python keyword from Python 3.6.
  Pexpect will still recognise async as an alternative spelling.
• Similarly, the module pexpect.async became pexpect._async
  (:ghpull:450). This module is not part of the public API.
• Fix problems with asyncio objects closing file descriptors during garbage
  collection (:ghissue:347, :ghpull:376).
• Set the .pid attribute of a :class:~.PopenSpawn object (:ghpull:417).
• Fix passing Windows paths to :class:~.PopenSpawn (:ghpull:446).
• :class:~.PopenSpawn on Windows can pass string commands through to Popen
  without splitting them into a list (:ghpull:447).
• Stop shlex trying to read from stdin when :class:~.PopenSpawn is
  passed cmd=None (:ghissue:433, :ghpull:434).
• Ensure that an error closing a Pexpect spawn object raises a Pexpect error,
  rather than a Ptyprocess error (:ghissue:383, :ghpull:386).
• Cleaned up invalid backslash escape sequences in strings (:ghpull:430,
  :ghpull:445).
• The pattern for a password prompt in :mod:pexpect.pxssh changed from
  password to password: (:ghpull:452).
• Correct docstring for using unicode with spawn (:ghpull:395).
• Various other improvements to documentation.

Got merge conflicts? Close this PR and delete the branch. I'll create a new PR for you.

Happy merging! 🤖