juju/api.go: actually handle error (bug #1312136)

juju/api.go: actually handle error (bug #1312136)

If there is a problem reading the .jenv file, it can return an error,
but we weren't paying attention to it. Instead we would end up getting a
panic() a few lines down when we go to use a *Config that is actually
nil.

This may not be perfect (because I wasn't seeing errors as I would
expect), but it is better than what we have.

https://code.launchpad.net/~jameinel/juju-core/1.18-panic-parsing-jenv-1312136/+merge/217036

(do not edit description out of merge proposal)

[jameinel, 2014-04-24 12:20:26]

Please take a look.

[jameinel, 2014-04-24 12:26:51]

Please take a look.

[wwitzel3, 2014-04-24 13:30:10]

LGTM

[wwitzel3, 2014-04-24 13:39:40]

Question

https://codereview.appspot.com/92750043/diff/20001/juju/api.go
File juju/api.go (right):

https://codereview.appspot.com/92750043/diff/20001/juju/api.go#newcode258
juju/api.go:258: var cfg *config.Config
What is the benefit of declaring these here? Instead of using := in the
config.New and envs.Config calls? It seems that declaring these here is what
prevents this being a compile time error (for unused err) instead of a run time
error for an unhandled panic?

[jameinel, 2014-04-24 13:55:14]

Please take a look.

[jameinel, 2014-04-24 14:14:11]

Please take a look.

[wwitzel3, 2014-04-24 14:24:39]

SGTM