Log Message:
py-paramiko: update to 3.4.0.

- :release:`3.4.0 <2023-12-18>`
- :feature:`-` `Transport` grew a new ``packetizer_class`` kwarg for overriding
  the packet-handler class used internally. Mostly for testing, but advanced
  users may find this useful when doing deep hacks.
- :bug:`-` Address `CVE 2023-48795<https://terrapin-attack.com/>`_ (aka the
  "Terrapin Attack", a vulnerability found in the SSH protocol re: \ 
treatment of
  packet sequence numbers) as follows:

    - The vulnerability only impacts encrypt-then-MAC digest algorithms in
      tandem with CBC ciphers, and ChaCha20-poly1305; of these, Paramiko
      currently only implements ``hmac-sha2-(256|512)-etm`` in tandem with
      ``AES-CBC``. If you are unable to upgrade to Paramiko versions containing
      the below fixes right away, you may instead use the
      ``disabled_algorithms`` connection option to disable the ETM MACs and/or
      the CBC ciphers (this option is present in Paramiko >=2.6).
    - As the fix for the vulnerability requires both ends of the connection to
      cooperate, the below changes will only take effect when the remote end is
      OpenSSH >= 9.6 (or equivalent, such as Paramiko in server mode, as of
      this patch version) and configured to use the new "strict kex" mode.
      Paramiko will always attempt to use "strict kex" mode if offered \ 
by the
      server, unless you override this by specifying ``strict_kex=False`` in
      `Transport.__init__`.
    - Paramiko will now raise an `SSHException` subclass (`MessageOrderError`)
      when protocol messages are received in unexpected order. This includes
      situations like receiving ``MSG_DEBUG`` or ``MSG_IGNORE`` during initial
      key exchange, which are no longer allowed during strict mode.
    - Key (re)negotiation -- i.e. ``MSG_NEWKEYS``, whenever it is encountered
      -- now resets packet sequence numbers. (This should be invisible to users
      during normal operation, only causing exceptions if the exploit is
      encountered, which will usually result in, again, `MessageOrderError`.)
    - Sequence number rollover will now raise `SSHException` if it occurs
      during initial key exchange (regardless of strict mode status).

  Thanks to Fabian Bäumer, Marcus Brinkmann, and Jörg Schwenk for submitting
  details on the CVE prior to release.

- :bug:`-` Tweak ``ext-info-(c|s)`` detection during KEXINIT protocol phase;
  the original implementation made assumptions based on an OpenSSH
  implementation detail.