Expose Errors during Authentication properly

[swissmanu]

As discovered here by @jhakonen in 777cfa7#commitcomment-15226112, provide a proper error handling during the first encounter with the potential hub.

[pponce]

First i want to say thanks for working on this project!
I wish i had the skills to contribute.
Any plans in the works to try and resolve this issue?
I think this error is causing homebridge to crash when used with the homebridge-harmonyhub plugin.
KraigM/homebridge-harmonyhub#61