Deprecate the vmwareapi driver

As of now, questions on the mailing list are going unanswered, and the
Nova team does not have a clear representative owner for the driver
to which bugs and other reports can be directed. There does not appear
to be a CI system running tests for the driver anymore, and the latest
indication from the community[1] points to it being potentially broken with
devstack.

This patch starts the deprecation timer for the driver and/or serves
as a flare to gauge interest (or lack thereof) in continuing to maintain
the driver.

1: http://lists.openstack.org/pipermail/openstack-discuss/2020-March/013066.html

Change-Id: Ie39e9605dc8cebff3795a29ea91dc08ee64a21eb

nova/virt/vmwareapi/driver.py

@@ -200,6 +200,13 @@ class VMwareVCDriver(driver.ComputeDriver):
                 self._datastore_regex = None
 
     def init_host(self, host):
+        LOG.warning('The vmwareapi driver is deprecated and may be removed in '
+                    'a future release. The driver is not tested by the '
+                    'OpenStack project nor does it have clear maintainer(s) '
+                    'and thus its quality can not be ensured. If you are '
+                    'using the driver in production please let us know in '
+                    'freenode IRC and/or the openstack-discuss mailing list.')
+
         vim = self._session.vim
         if vim is None:
             self._session._create_session()

releasenotes/notes/deprecate-vmware-ussuri-39e0215eca80ffd7.yaml

@@ -0,0 +1,6 @@
+---
+deprecations:
+  - |
+    The vmwareapi driver is deprecated in this release and may be
+    removed in a future one. The driver is not tested by the OpenStack
+    Nova project and does not have a clear maintainer.