Tab complete causes traceback when trying to tab-complete juju commands

[Jeff Lane ]

Example:

juju debug-hooks -<tab tab>

results in this:

juju debug-hooks -Traceback (most recent call last):
  File "<string>", line 5, in <module>
KeyError: 'services'

And it just seems to sit there until I either Ctrl-C or hit Enter. If I hit Enter, I get this:

juju debug-hooks -Traceback (most recent call last):
  File "<string>", line 5, in <module>
KeyError: 'services'

error: "-" is not a valid unit name

In most commands, tab complete either displays the available - options (e.g. -m) or it does nothing at all. But this should not be generating a traceback.

juju:
  Installed: 2.0-beta13~20160719~4146~8fb2713b-20160719+4146+8fb2713b~16.04
  Candidate: 2.0-beta13~20160719~4146~8fb2713b-20160719+4146+8fb2713b~16.04