Comment 2 for bug 1889646

The error is coming from snap-confine (low-lever helper used for sandboxing when snap is run); it is only printed if there is an issue creating user snap data directory under $SNAP_USER_DATA.

In this case user is root and I think we may have a bug in snap-confine as it assumes "/home" and doesn't consider "/root", however this doesn't explain the root cause (which is an issue with creating snap data dir). As for the root cause, looking at the snap.yaml of maas, the layout bit looks a bit suspicious and I wonder if it could be the troublemaker:

layout:
   ...
  /root:
    bind: $SNAP_DATA/root