Some properties don't work inside snap confinement

[benfrancis]

It was reported here that this add-on can be installed on WebThings Gateway 2.0 running inside a snap and some properties work but temperature and battery are shown as zero.

What commands are used to report those values? I might need to add a new interface to the gateway snap, or the add-on might need to change how it gets these values inside snap confinement.

[benfrancis]

Network info will probably need to use Network Manager when run inside a snap.