Code review comment for lp:~wallyworld/juju-core/marshal-image-metadata

Reviewers: mp+190542_code.launchpad.net,

Message:
Please take a look.

Description:
Write image metadata using json serialisation

This branch writes outs simplestreams image metadata using
json serialisation instead of a template based approach. It
is a pre-requisit to allow the next step of merging new image
metadata instead of overwriting. This will be used when setting
up private clouds.

https://code.launchpad.net/~wallyworld/juju-core/marshal-image-metadata/+merge/190542

Requires:
https://code.launchpad.net/~wallyworld/juju-core/improve-image-metadata-command/+merge/190517

(do not edit description out of merge proposal)

Please review this at https://codereview.appspot.com/14540055/

Affected files (+398, -135 lines):
   A [revision details]
   M cmd/plugins/juju-metadata/imagemetadata.go
   M environs/imagemetadata/generate.go
   A environs/imagemetadata/generate_test.go
   A environs/imagemetadata/marshal.go
   A environs/imagemetadata/marshal_test.go
   M environs/imagemetadata/simplestreams.go
   A environs/imagemetadata/testing/testing.go
   M environs/imagemetadata/validation_test.go
   M environs/simplestreams/simplestreams.go
   M environs/tools/marshal.go