made sure NA is option of last resort

Fix envvars support in openstack modules

Add -Compress to ConvertTo-Json calls in common powershell code

limit extensions for files in group/host_vars dir

Include more info when a task fails

Add required_if to AnsibleModule

Adds "playbook", "role", and "task" fields to the output when a task fails.

This makes it easier to pinpoint where the problem is, especially
when you have a lot of roles and playbooks.

e.g.:

    failed: [vagrant] => {..."playbook": "/Users/marca/dev/ansible/vagrant.yml",
                          ..."role": "pythonapp",
                          ..."task": "pip install -r /opt/src/{{ sm_app_role }}/requirements.txt"...}

Setting LC_MESSAGES: prevent unparseable messages (fixes issue #9635)

Remove duplicate RETRY_FILES_* constants

fix typo in --ask-sudo-pass reference within playbook_intro doc

only files with extensions as per
C.YAML_FILENAME_EXTENSIONS should be parsed

inventory vars: make loading from a directory obey the same rules as
when checking the base paths, looking at the file name extensions
as defined in CONSTANTS.YAML_FILENAME_EXTENSIONS

Fixes Github issue #11017

Minor Fix for broken link