---
features:
  - |
    Support for accessing configuration data in environment variables via the
    environment backend driver, enabled by default. The environment is checked
    after command line options, but before configuration files.

    Environment variables are checked for any configuration data. The variable
    names take the form:

    * A prefix of ``OS_``
    * The group name, uppercased
    * Separated from the option name by a `__` (double underscore)
    * Followed by the name

    For an option that looks like this in the usual INI format::

        [placement_database]
        connection = sqlite:///

    the corresponding environment variable would be
    ``OS_PLACEMENT_DATABASE__CONNECTION``.