Fix error handling in fetch

[aredridel]

This converts fetch errors into actual errors, which should prevent authorization failure response bodies from being passed as authorization tokens to future requests

[aredridel]

This should also keep this project in the owners of the API's good graces too.

[bewest]

Looks good, sorry for getting around to this so late. You may be interested in this as well: https://github.com/nightscout/nightscout-connect.
Since request is deprecated, I'm looking at replacing the headache of managing m plugins to just 1.

[aredridel]

I will check that out!

[aredridel]

Looks like that version is unaffected since axios's defaults are to throw if status code is < 100 or >= 300.