Mention Watcher dependency when creating 3rd-party plugins

[Vincent Françoise]

In the base-setup.rst doc about how to create a 3rd party project for implementing a Watcher plugin, we are not mentioning the fact that we need to put the python-watcher pypi package as a dependency in the requirements.txt file of the 3rd party.

We need to add an extra paragraph to explicit this.

This bug is the conclusion of the following conversation: http://eavesdrop.openstack.org/irclogs/%23openstack-watcher/%23openstack-watcher.2016-06-21.log.html#t2016-06-21T07:32:33

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/334800

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/334800
Committed: https://git.openstack.org/cgit/openstack/watcher/commit/?id=d03e1d54bd357cb22c4d23a925e8f26c331a4942
Submitter: Jenkins
Branch: master

commit d03e1d54bd357cb22c4d23a925e8f26c331a4942
Author: licanwei <email address hidden>
Date: Tue Jun 28 15:13:13 2016 +0800

    add dependency for 3rd-party plugins

    In the base-setup.rst about 3rd-party plugins,
    we should add the watcher dependency requirement.

    Change-Id: I8f898b2e3e7e30c88f4f14f7bd3ae38b8aa3ebd3
    Closes-Bug: #1594705

[Doug Hellmann (doug-hellmann)]

This issue was fixed in the openstack/watcher 0.28.0 release.