Show same error for no default env

Show same error for no default env

When you run juju with no default config file, it should give the same error regardless of the command you're running. To do that, I have ReadEnviron wrap the file not found error it used to return in a new type, so that further up the stack we can check for it, and notify the user appropriately.

https://code.launchpad.net/~natefinch/juju-core/juju-core/+merge/178288

(do not edit description out of merge proposal)

[dimitern, 2013-08-05 12:19:11]

LGTM, apart from a few trivial suggestions below

https://codereview.appspot.com/12347044/diff/1/cmd/juju/init.go
File cmd/juju/init.go (right):

https://codereview.appspot.com/12347044/diff/1/cmd/juju/init.go#newcode8
cmd/juju/init.go:8: "launchpad.net/gnuflag"
While you're at it, please reformat the imports here:

"fmt"

"launchpad.net/gnuflag"

"launchpad.net/juju-core/..."

We accepted this style of formatting imports some time ago and we should take
the time to fix old code to use the new convention: 1) standard pacakges, 2)
third-parties, 3) juju-core stuff, each group separated with a blank line from
the previous.

https://codereview.appspot.com/12347044/diff/1/environs/config.go
File environs/config.go (right):

https://codereview.appspot.com/12347044/diff/1/environs/config.go#newcode141
environs/config.go:141: if path == "" && os.IsNotExist(err) {
I don't think you need to check path == "" here, because environsPath will
actually handle that and set it to the default.

https://codereview.appspot.com/12347044/diff/1/errors/errors.go
File errors/errors.go (right):

https://codereview.appspot.com/12347044/diff/1/errors/errors.go#newcode68
errors/errors.go:68: // NoEnvError indicates the default environment config file
is missing
s/missing/missing./

https://codereview.appspot.com/12347044/diff/1/errors/errors.go#newcode73
errors/errors.go:73: // IsNoEnv returns true if err is a NoEnvError
By convention, such functions we usually document as "F returns if/whether/etc
...", no need to say it returns true. Also there should be a full stop at the
end.

[natefinch, 2013-08-05 17:35:59]

Fixed dimitern's suggestions, also took rogpeppe's suggestions to remove the
changes to cmd.go and put the error check in each command instead.

[natefinch, 2014-04-24 19:50:07]

Please take a look.

[natefinch, 2014-04-24 19:54:47]

Please take a look.

[natefinch, 2014-04-24 20:11:49]

Please take a look.

[natefinch, 2014-04-24 20:13:05]

Please take a look.