add credstash lookup plugin

[scottcunningham]

Credstash is a small utility for managing secrets using AWS's KMS and DynamoDB: https://github.com/LuminalOSS/credstash

Example usage:

- name: "Test credstash lookup plugin"
  debug: msg="Credstash lookup! {{ lookup('credstash', 'my-github-password') }}"

All credstash options (region, table, etc) are also configurable:

- name: "Test credstash lookup plugin"
  debug: msg="Credstash lookup! {{ lookup('credstash', 'my-other-password', region='us-west-1') }}"

I have some small questions about contributing. This lookup plugin has a dependency on the credstash module. Is there a way for me to add this as a dependency for the plugin? Is there also a good way for me to add documentation?

[bcoca]

we should capture possible import exception and explain that this lookup requires the credstash python library when it fails

[bcoca]

for documentation add it and an example to docsites/rst//playbooks_lookups.rst

[scottcunningham]

Great, thanks a lot for the feedback @bcoca. I've added both now. The build is failing but it looks unrelated to me:

Compiling lib/ansible/module_utils/vmware.py ...
  File "lib/ansible/module_utils/vmware.py", line 125
    except vim.fault.InvalidLogin as invalid_login:

[scottcunningham]

Fixed exception handling syntax that would've caused an error in Python 2.4.

Could I get an update on this please? Is there anything else that I can do to help move this forward?

[bcoca]

no, sorry, just for us to have enough time to review and merge

[bcoca]

this should be in the run method, otherwise ansible itself will fail to run

[abadger]

By this we mean the

if not CREDSTASH_INSTALLED:
    raise AnsibleError([...])

If importring credstash takes a long time it might be good to move that to inside the lookup module as well but that's an unrelated issue.

[scottcunningham]

Very good point - thanks! I've moved this to inside of the run function.

I don't think that credstash takes a particularly long time to import, but if you feel it'd be best to keep it inside the module then I can move it there.

[abadger]

Lookup plugins run on the controller. The minimum python version for the controller is python 2.6. So str.format() can't use "{}". The easy workaround is to use "{0}" and "{1}" instead.

[scottcunningham]

Good point - I've updated the PR to fix this.

[scottcunningham]

Update - I've fixed the issues raised above. Thanks a lot for taking the time to check this out.

[scottcunningham]

Thank you! :)