Make control-bucket optional.

Make control-bucket optional.

The existing function get_admin_secret is made generic and the name is changed
to get_value_from_jenv.  It now takes a keyname to be fetched from the
generated file.

For both ec2 and openstack the control-bucket field has been made optional
with respect to the environments.yaml file.

QA:

1) Create an ec2 environment with no control-bucket.
2) Bootstrap that environment.  Ensure a control-bucket is in the .jenv file.
3) Run quickstart and see that it uses the existing environment and does not
raise an error.

https://code.launchpad.net/~bac/juju-quickstart/1309678/+merge/216634

(do not edit description out of merge proposal)

[bac, 2014-04-21 21:14:45]

Please take a look.

[frankban, 2014-04-22 09:01:40]

Hi Brad,

this branch looks nice.
As you mentioned, I am not sure why we want to retrieve the control bucket from
the jenv: while quickstart needs the admin secret so that it can connect to the
Juju API, the control bucket has no use, except validating the jenv file, which
I think we can assume to be correctly generated by juju-core.

What do you think about the following?
1) we just mark the control bucket fields as optional in the ec2 and openstack
metadata;
2) in newer juju-core version, a missing value should just work;
3) in older juju-core, I'd expect bootstrap to exit with an error, and the user
can still use quickstart to set the value;
4) in both cases, if bootstrap succeeds, we can continue the process without
checking the control-bucket value in the jenv.

I expect the above to simplify this branch a lot.
What do you think?

https://codereview.appspot.com/90060043/diff/1/quickstart/manage.py
File quickstart/manage.py (right):

https://codereview.appspot.com/90060043/diff/1/quickstart/manage.py#newcode481
quickstart/manage.py:481: control_bucket = options.control_bucket
AFAICT the control bucket is never set in the options namespace. For this
reason. I'd expect this to raise an AttributeError in the unlikely case the
value is not in the jenv, but maybe I am missing something.

Anyway, I am concerned about the need to retrieve the control bucket.
Please see my comment.

[bac, 2014-04-22 12:35:20]

Please take a look.

[frankban, 2014-04-22 12:52:04]

LGTM QA ok.

[bac, 2014-04-22 13:17:14]

*** Submitted:

Make control-bucket optional.

The existing function get_admin_secret is made generic and the name is changed
to get_value_from_jenv.  It now takes a keyname to be fetched from the
generated file.

For both ec2 and openstack the control-bucket field has been made optional
with respect to the environments.yaml file.

QA:

1) Create an ec2 environment with no control-bucket.
2) Bootstrap that environment.  Ensure a control-bucket is in the .jenv file.
3) Run quickstart and see that it uses the existing environment and does not
raise an error.

R=frankban
CC=
https://codereview.appspot.com/90060043