RMCP support broken in 0.5.8

[patrislav1]

The update from 0.5.7 to 0.5.8 breaks RMCP support.

Any code that uses python-ipmi in RMCP mode will abort with this error:

  File "/home/huesmann/src/mmcterm/.venv/lib/python3.12/site-packages/pyipmi/session.py", line 118, in establish
    self.interface.establish_session(self)
  File "/home/huesmann/src/mmcterm/.venv/lib/python3.12/site-packages/pyipmi/interfaces/rmcp.py", line 523, in establish_session
    self.ping()
  File "/home/huesmann/src/mmcterm/.venv/lib/python3.12/site-packages/pyipmi/interfaces/rmcp.py", line 464, in ping
    self._send_asf_msg(ping)
  File "/home/huesmann/src/mmcterm/.venv/lib/python3.12/site-packages/pyipmi/interfaces/rmcp.py", line 451, in _send_asf_msg
    self._send_rmcp_msg(msg.pack(), RMCP_CLASS_ASF)
  File "/home/huesmann/src/mmcterm/.venv/lib/python3.12/site-packages/pyipmi/interfaces/rmcp.py", line 419, in _send_rmcp_msg
    self._sock.sendto(pdu, (self.host, self.port))
    ^^^^^^^^^^
AttributeError: 'Rmcp' object has no attribute '_sock'

A minimal snippet to reproduce the error can be taken straight from the documentation:

import pyipmi
import pyipmi.interfaces

interface = pyipmi.interfaces.create_interface(
    interface="rmcp",
    slave_address=0x81,
    host_target_address=0x20,
    keep_alive_interval=1,
)
ipmi = pyipmi.create_connection(interface)
ipmi.session.set_session_type_rmcp(host="10.0.114.199", port=623)
ipmi.session.set_auth_type_user(username="admin", password="admin")

ipmi.target = pyipmi.Target(ipmb_address=0x20)

ipmi.session.establish()
device_id = ipmi.get_device_id()

The last commit on the RCMP interface moved the socket initialization from the constructor to a dedicated open() method, but it is unclear how to trigger that logic or if you're even supposed to call it explicitly as a user.

Let me know if I can do anything to help fix this bug.

[patrislav1]

Update: The bug can be worked around by explicitly calling open() on the interface before establishing the session. However, I'm not sure if this is as intended/expected (then at least the documentation should be updated IMHO).