Get admin_secret from juju-generated jenv file.

Get admin_secret from juju-generated jenv file.

As of Juju v 1.17 the admin-secret is stored in a generated file, located in
$JUJU_HOME/environments/<environment>.jenv.

If an admin-secret is provided in environments.yaml, it is used and also
stored in the jenv file.  If none is given, then juju fabricates one and
stores it in the jenv file.

The admin-secret *field* is marked as optional now.  For the case where a
local environment is used, Quickstart previously would generate an
admin-secret.  That behavior is maintained by forcing 'admin-secret' to be in
the missing_fields list.  This approach ensures backwards compatibility.

Note that the Juju-generated admin-secret is not available until after
bootstrapping the environment.  Due to this behavior, when using juju v1.16
and not admin-secret is configured in the environments.yaml file, the failure
will not be reported until after bootstrapping.  This approach seemed better
than introducing hard version checking.

https://code.launchpad.net/~bac/juju-quickstart/auth/+merge/203631

(do not edit description out of merge proposal)

[bac, 2014-01-28 20:51:54]

Please take a look.

[frankban, 2014-01-29 11:48:39]

This branch is nice Brad, thank you.
LGTM with minor changes and a less trivial suggestion I'd like you to consider.

https://codereview.appspot.com/57900043/diff/1/quickstart/manage.py
File quickstart/manage.py (right):

https://codereview.appspot.com/57900043/diff/1/quickstart/manage.py#newcode294
quickstart/manage.py:294: At bootstrap, juju (v1.17 and later) writes the
admin-secret to a
IIRC Jenv files are generated starting form v1.16.

https://codereview.appspot.com/57900043/diff/1/quickstart/manage.py#newcode309
quickstart/manage.py:309: raise ValueError('admin-secret not found in
{}.'.format(filename))
Please encode('utf-8') the ValueError message.

https://codereview.appspot.com/57900043/diff/1/quickstart/manage.py#newcode316
quickstart/manage.py:316: - admin_secret: the password to use to access the Juju
API;
... or None if the admin-secret field is not found in the environments YAML
file... or similar?

https://codereview.appspot.com/57900043/diff/1/quickstart/manage.py#newcode419
quickstart/manage.py:419: options.admin_secret = _get_admin_secret(
It seems _get_admin_secret can raise exceptions we never catch. I am considering
a different strategy for this, please let me know what you think about the
following:
We always try to parse the jenv file, even if we already have an admin_secret.
Subsequently, we make the following check:
- if the password is found in the jenv, we use that, done.
- if the password is not found in the jenv:
  - if we already have an admin secret, we use that;
  - othrwise we exit with a (nice) error.
As a side note, this can involve moving the _get_admin_secret function to the
app module.
AFAICT this way we achieve two goals:
- we are still backward compatible with old versions of Juju;
- we support a use case we don't currently handle (in trunk): the case when a
user has a jenv enabled juju-core, runs quickstart to bootstrap an environment,
then runs quickstart interactively to explicitly provide an admin-secret, and
then re-invoke quickstart again on the same environment (say, in order to deploy
a bundle or reopen the GUI). Now the passwords from the environments file and
from the jenv are not the same, but since we made the latter override the
former, everything works well.
How does it sound?

Another, less important, suggestion follows.
Rather than modifying options, we might just define admin_secret in this scope,
e.g.:

admin_secret = options.admin_secret
if admin_secret is None:
   admin_secret = ...

And then s/options.admin_secret/admin_secret/ below. 
This way we keep the (very weak) separation between setup (which sets up
options) and run (which just uses them). <shrug>

https://codereview.appspot.com/57900043/diff/1/quickstart/models/envs.py
File quickstart/models/envs.py (right):

https://codereview.appspot.com/57900043/diff/1/quickstart/models/envs.py#newc...
quickstart/models/envs.py:177: contents = _load_file(env_file)
Very nice.

[bac, 2014-01-29 21:10:01]

Please take a look.

https://codereview.appspot.com/57900043/diff/1/quickstart/manage.py
File quickstart/manage.py (right):

https://codereview.appspot.com/57900043/diff/1/quickstart/manage.py#newcode294
quickstart/manage.py:294: At bootstrap, juju (v1.17 and later) writes the
admin-secret to a
On 2014/01/29 11:48:40, frankban wrote:
> IIRC Jenv files are generated starting form v1.16.

Done.

https://codereview.appspot.com/57900043/diff/1/quickstart/manage.py#newcode309
quickstart/manage.py:309: raise ValueError('admin-secret not found in
{}.'.format(filename))
On 2014/01/29 11:48:40, frankban wrote:
> Please encode('utf-8') the ValueError message.

Done.

https://codereview.appspot.com/57900043/diff/1/quickstart/manage.py#newcode316
quickstart/manage.py:316: - admin_secret: the password to use to access the Juju
API;
On 2014/01/29 11:48:40, frankban wrote:
> ... or None if the admin-secret field is not found in the environments YAML
> file... or similar?

Done.

https://codereview.appspot.com/57900043/diff/1/quickstart/manage.py#newcode419
quickstart/manage.py:419: options.admin_secret = _get_admin_secret(
Good idea.  I've moved the definition of get_admin_secret to app.

[bac, 2014-01-29 21:21:09]

*** Submitted:

Get admin_secret from juju-generated jenv file.

As of Juju v 1.17 the admin-secret is stored in a generated file, located in
$JUJU_HOME/environments/<environment>.jenv.

If an admin-secret is provided in environments.yaml, it is used and also
stored in the jenv file.  If none is given, then juju fabricates one and
stores it in the jenv file.

The admin-secret *field* is marked as optional now.  For the case where a
local environment is used, Quickstart previously would generate an
admin-secret.  That behavior is maintained by forcing 'admin-secret' to be in
the missing_fields list.  This approach ensures backwards compatibility.

Note that the Juju-generated admin-secret is not available until after
bootstrapping the environment.  Due to this behavior, when using juju v1.16
and not admin-secret is configured in the environments.yaml file, the failure
will not be reported until after bootstrapping.  This approach seemed better
than introducing hard version checking.

R=frankban
CC=
https://codereview.appspot.com/57900043