* - Throw ClassCastException instead of NullPointerException, as documented in the current
       *   Javadoc. (Note that we can't necessarily "just" change our call to `getProperty` to `get`
       *   because `get` does not consult the default properties.)
       */
      builder.put(key, requireNonNull(properties.getProperty(key)));
    }

    return builder.buildOrThrow();
  }

  /**

       * - Throw ClassCastException instead of NullPointerException, as documented in the current
       *   Javadoc. (Note that we can't necessarily "just" change our call to `getProperty` to `get`
       *   because `get` does not consult the default properties.)
       */
      builder.put(key, requireNonNull(properties.getProperty(key)));
    }

    return builder.buildOrThrow();
  }

  /**

## External Dependency Version Information

Continuous integration builds have used the following versions of external dependencies, however, this is not a strong recommendation and users should consult an appropriate installation or upgrade guide before deciding what versions of etcd, docker or rkt to use.

* Docker versions 1.10.3 - 1.12.3
  * Docker version 1.11.2 known issues