Put bad attribute back

[jpobley]

The current fix for backwards compatibility breaks the logout flow.

traitlets will ignore any attribute in jupyterhub_config.py that's not defined on the class. When the typo was fixed, it meant that the bad attribute name couldn't be set on the class anymore.

Currently, when the user logs out, the authenticator will check it and raise an AttributeError, sending a 500: Internal Server Error to the UI.

[I 2020-04-21 21:05:01.922 JupyterHub samlauthenticator:732] User logged out: test.user
[E 2020-04-21 21:05:01.927 JupyterHub web:1792] Uncaught exception GET /hub/logout (::ffff:172.19.0.1)
    HTTPServerRequest(protocol='http', host='localhost:8000', method='GET', uri='/hub/logout', version='HTTP/1.1', remote_ip='::ffff:172.19.0.1')
    Traceback (most recent call last):
      File "/usr/local/lib/python3.6/dist-packages/tornado/web.py", line 1703, in _execute
        result = await result
      File "/usr/local/lib/python3.6/dist-packages/samlauthenticator/samlauthenticator.py", line 754, in get
        forwad_on_logout = True if authenticator_self.slo_forwad_on_logout else False
    AttributeError: 'SAMLAuthenticator' object has no attribute 'slo_forwad_on_logout'

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Signed-off-by: JP Obley jpobley@gmail.com

[distortedsignal]

Good catch. Is there a way that we can check this in a test?

[jpobley]

Good catch. Is there a way that we can check this in a test?

Hmmm. A test for the configuration or the handler? Testing configuration feels like we'd be testing traitlets. Your instinct is right, though: this bug definitely would have been caught by a test case for the handler.

Writing a test for any of the handlers is made complicated by the handlers themselves being defined in the SAMLAuthenticator.get_handlers() method. We could move the handler definitions out of that function, either to a new module or keep them in the same one, and then have their __init__ methods take the authenticator instance as an argument.

What do you think? It would increase the size of this PR, but I can take a stab at it between changing diapers.

[distortedsignal]

Nah - I think this is fine. Thanks for the work. I'll try to get this up later today.