Give support for new Mistral environment variables when installing the undercloud.

Sometimes developers will need to use additional values inside Mistral tasks. For example, if we need to create a dump of a database we might need another one than the Mistral user credentials for authentication purposes.

Initially when the Undercloud is installed it’s created a Mistral environment called tripleo.undercloud-config. This environment variable will have all required configuration details that we can get from Mistral. This is defined in the instack-undercloud repository.

Let’s get into the repository and check the content of the file instack_undercloud/undercloud.py.

This file defines a set of methods to interact with the Undercloud, specifically the method called _create_mistral_config_environment allows to configure additional environment variables when installing the Undercloud.

For additional testing, you can use the Python snippet to call Mistral client from the Undercloud node available in gist.github.com.