Error on raspberry pi 3 about networkmanager-wifi-webui

[mk-fg]

Failed to query NetworkManager dbus interface

Weird that it's not fatal, should've failed on boot if it couldn't connect to NM's dbus.

exceptions.AttributeError: 'NoneType' object has no attribute 'startswith'

This looks like a symptom of issue above - probably didn't test handling for connection errors like that, which should not normally allow the thing to be started, and should be otherwise fatal anyway.

Not sure if it's a problem with your setup or maybe if code have bitrotten to the point of not working anymore (due to e.g. NM changing dbus interface names recently, or such), as I don't use neither NM nor this interface myself (and don't know of any projects/places that use both).

If raspbian ships recent enough systemd version, I'd suggest using its nice busctl tool to see if NM is connected to dbus properly and has that org.freedesktop.NetworkManager interface registered there (or if it maybe changed to e.g. NetworkManager1 or something).

Not sure if I'll be of much more help than that, I'm afraid.
Can probably flash jessie and look into it sometime, but don't really have enough time as it is these days, unfortunately, so that's highly unlikely.

[mk-fg]

Not sure if it's a problem with your setup or maybe if code have bitrotten to the point of not working anymore

Btw, if you'll confirm if it's one way or the other, please report, will put a warning to the README for the others, at least.