juju panic()s when pwd is not readable

[Tycho Andersen]

root@ubuntu:~# sudo -u tycho juju
panic: version: cannot read forced version: open FORCE-VERSION: permission denied

goroutine 1 [running]:
launchpad.net/juju-core/version.init·1()
 /build/buildd/juju-core-1.13.3/src/launchpad.net/juju-core/version/version.go:58 +0x21c
launchpad.net/juju-core/version.init()
 /build/buildd/juju-core-1.13.3/src/launchpad.net/juju-core/version/version.go:297 +0x13c
launchpad.net/juju-core/tools.init()
 /build/buildd/juju-core-1.13.3/src/launchpad.net/juju-core/tools/tools.go:23 +0x4d
main.init()
 /build/buildd/juju-core-1.13.3/src/launchpad.net/juju-core/cmd/juju/upgradejuju.go:283 +0x43

goroutine 2 [runnable]:
root@ubuntu:~# pwd
/root
root@ubuntu:~# juju --version
1.13.3-raring-amd64

[Robert Ayres (robert-ayres)]

I'm not sure what FORCE-VERSION mechanism is actually used for, but the implementation seems odd to me.
Surely a FORCE-VERSION option would make more sense as a file in the user's .juju directory or an environment variable?