Nice info message if not on correct network?

[rsignell-usgs]

I forgot to get on the VPN, and of course errored out with "No address associated with hostname". Would it be a common enough user issue to issue an Info comment back of something like "Not found on current network. Do you need to be on your VPN?" or something?

************************************************************************************** Authenticating **************************************************************************************
Authenticating user (rsignell) from client (IGSAGIEGLTRSI10) to remote host (denali.cr.usgs.gov)
Traceback (most recent call last):
  File "/home/rsignell/mambaforge/envs/jupyter/bin/jupyter-forward", line 33, in <module>
    sys.exit(load_entry_point('jupyter-forward', 'console_scripts', 'jupyter-forward')())
  File "/home/rsignell/github/jupyter-forward/jupyter_forward/cli.py", line 103, in main
    typer.run(app())
  File "/home/rsignell/mambaforge/envs/jupyter/lib/python3.10/site-packages/typer/main.py", line 214, in __call__
    return get_command(self)(*args, **kwargs)
  File "/home/rsignell/mambaforge/envs/jupyter/lib/python3.10/site-packages/click/core.py", line 1128, in __call__
    return self.main(*args, **kwargs)
  File "/home/rsignell/mambaforge/envs/jupyter/lib/python3.10/site-packages/click/core.py", line 1053, in main
    rv = self.invoke(ctx)
  File "/home/rsignell/mambaforge/envs/jupyter/lib/python3.10/site-packages/click/core.py", line 1395, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/rsignell/mambaforge/envs/jupyter/lib/python3.10/site-packages/click/core.py", line 754, in invoke
    return __callback(*args, **kwargs)
  File "/home/rsignell/mambaforge/envs/jupyter/lib/python3.10/site-packages/typer/main.py", line 500, in wrapper
    return callback(**use_params)  # type: ignore
  File "/home/rsignell/github/jupyter-forward/jupyter_forward/cli.py", line 88, in start
    runner = RemoteRunner(
  File "<string>", line 12, in __init__
  File "/home/rsignell/github/jupyter-forward/jupyter_forward/core.py", line 60, in __post_init__
    self._authenticate()
  File "/home/rsignell/github/jupyter-forward/jupyter_forward/core.py", line 76, in _authenticate
    self.session.open()
  File "/home/rsignell/mambaforge/envs/jupyter/lib/python3.10/site-packages/fabric/connection.py", line 636, in open
    self.client.connect(**kwargs)
  File "/home/rsignell/mambaforge/envs/jupyter/lib/python3.10/site-packages/paramiko/client.py", line 340, in connect
    to_try = list(self._families_and_addresses(hostname, port))
  File "/home/rsignell/mambaforge/envs/jupyter/lib/python3.10/site-packages/paramiko/client.py", line 203, in _families_and_addresses
    addrinfos = socket.getaddrinfo(
  File "/home/rsignell/mambaforge/envs/jupyter/lib/python3.10/socket.py", line 955, in getaddrinfo
    for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
socket.gaierror: [Errno -5] No address associated with hostname

[kmpaul]

That sounds reasonable. It's an error coming from Python's builtin socket module indicating a DNS resolution error, I think. That could happen due to a typo in the domain name, too.

Should we catch the error in Jupyter-forward and reraise an error with a better message? Or should we propose an improved error message upstream? If so, where? Paramiko?

[kmpaul]

CC @mnlevy1981 @andersy005