def check_auth_interactive(self, username, submethods):
return AUTH_FAILED<EOL>
Begin an interactive authentication challenge, if supported.  You
should override this method in server mode if you want to support the
C{"keyboard-interactive"} auth type, which requires you to send a
series of questions for the client to answer.

Return L{AUTH_FAILED} if this auth method isn't supported.  Otherwise,
you should return an L{InteractiveQuery} object containing the prompts
and instructions for the user.  The response will be sent via a call
to L{check_auth_interactive_response}.

The default implementation always returns L{AUTH_FAILED}.

@param username: the username of the authenticating client
@type username: str
@param submethods: a comma-separated list of methods preferred by the
    client (usually empty)
@type submethods: str
@return: L{AUTH_FAILED} if this auth method isn't supported; otherwise
    an object containing queries for the user
@rtype: int or L{InteractiveQuery}