Make simplestreams metadata loading more robust

Make simplestreams metadata loading more robust

When looking at each base URL to try and load the simplestreams
metadata, unauthorised errors would be considered fatal and abort
the search. This branch makes such errors similar to not found
errors in that the next URL is attempted.

https://code.launchpad.net/~wallyworld/juju-core/simplestream-url-errors/+merge/166442

Requires: https://code.launchpad.net/~wallyworld/juju-core/consolidate-common-errors/+merge/166415

(do not edit description out of merge proposal)

[wallyworld, 2013-05-30 05:44:51]

Please take a look.

[jameinel, 2013-05-30 06:05:25]

LGTM

[dimitern, 2013-05-30 11:42:04]

LGTM with one suggestion.

https://codereview.appspot.com/9666050/diff/1/environs/imagemetadata/simplest...
File environs/imagemetadata/simplestreams.go (right):

https://codereview.appspot.com/9666050/diff/1/environs/imagemetadata/simplest...
environs/imagemetadata/simplestreams.go:214: func
getMaybeSignedImageIdMetadata(baseURLs []string, indexPath string, ic
*ImageConstraint, requireSigned bool) ([]*ImageMetadata, error) {
now that's a method name that tells a whole story :)

https://codereview.appspot.com/9666050/diff/1/environs/imagemetadata/simplest...
environs/imagemetadata/simplestreams.go:255: return nil, dataURL,
errors.Unauthorizedf("unauthorised access to URL %q", dataURL)
let's stick to one form: unauthorized or unauthorised - i prefer the former.

[wallyworld, 2013-05-31 01:37:12]

*** Submitted:

Make simplestreams metadata loading more robust

When looking at each base URL to try and load the simplestreams
metadata, unauthorised errors would be considered fatal and abort
the search. This branch makes such errors similar to not found
errors in that the next URL is attempted.

R=jameinel, dimitern
CC=
https://codereview.appspot.com/9666050

[wallyworld, 2013-05-31 01:40:37]

On 2013/05/30 11:42:04, dimitern wrote:
> LGTM with one suggestion.
> 
>
https://codereview.appspot.com/9666050/diff/1/environs/imagemetadata/simplest...
> File environs/imagemetadata/simplestreams.go (right):
> 
>
https://codereview.appspot.com/9666050/diff/1/environs/imagemetadata/simplest...
> environs/imagemetadata/simplestreams.go:214: func
> getMaybeSignedImageIdMetadata(baseURLs []string, indexPath string, ic
> *ImageConstraint, requireSigned bool) ([]*ImageMetadata, error) {
> now that's a method name that tells a whole story :)
> 
>
https://codereview.appspot.com/9666050/diff/1/environs/imagemetadata/simplest...
> environs/imagemetadata/simplestreams.go:255: return nil, dataURL,
> errors.Unauthorizedf("unauthorised access to URL %q", dataURL)
> let's stick to one form: unauthorized or unauthorised - i prefer the former.

Ah I forgot to fix this before submitting :-( I'll do it as a driveby in another
branch.
"unauthorised" is the correct spelling as that's the proper Queen's English used
in UK and Australia and elsewhere all over the world. The z form is the American
spelling.
But sadly Go uses the z form (eg http.Unauthorized) so I guess we have to stick
to that :-(