Comment 1 for bug 1303880

If you upgrades from 1.16.x, then the local permissions are wrong. Per the 1.18.0 release notes.

If you have used the local provider before, you may need to manually
clean up some files that are still owned by root. The environment’s jenv
file commonly needs to be removed. If your local environment is named
"local" then there may be a local.jenv owned by root with the JUJU_HOME
directory (~/.juju). After the local environment is destroyed, you can
remove the file like this

    $ sudo rm ~/.juju/environments/local.jenv