Some examples of plugins invoking stuff, direct execution: https://github.com/toddgardner/pants-plugins/blob/d8a7a4647dac10ddf453ff0f59fba6a648672883/src/python/verst/pants/docker/docker_base_task.py#L19 running a JVM program: https://github.com/toddgardner/pants-plugins/blob/master/src/python/verst/pants/specs2/task.py#L89