conf: Deprecated 'config_drive_format'

This is no longer necessary with our current minimum libvirt version.

Change-Id: Id2beaa7c4e5780199298f8e58fb6c7005e420a69
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>

nova/conf/configdrive.py

@@ -15,13 +15,15 @@
 from oslo_config import cfg
 
 config_drive_opts = [
-    # TODO(stephenfin): We should deprecate this, given that it was originally
-    # added to workaround [1] which was fixed in libvirt v1.2.17 [2]
-    #
-    # [1] https://bugs.launchpad.net/nova/+bug/1246201
-    # [2] https://bugzilla.redhat.com/show_bug.cgi?id=1203032
     cfg.StrOpt('config_drive_format',
         default='iso9660',
+        deprecated_for_removal=True,
+        deprecated_since='19.0.0',
+        deprecated_reason="""
+This option was originally added as a workaround for bug in libvirt, #1246201,
+that was resolved in libvirt v1.2.17. As a result, this option is no longer
+necessary or useful.
+""",
         choices=[
             ('iso9660', 'A file system image standard that is widely '
              'supported across operating systems.'),

releasenotes/notes/deprecate-config_drive_format-62d481260c254187.yaml

@@ -0,0 +1,8 @@
+---
+deprecations:
+  - |
+    The ``config_drive_format`` config option has been deprecated. This was
+    necessary to workaround an issue with libvirt that was later resolved in
+    libvirt v1.2.17. For more information refer to `bug #1246201`__.
+
+    __ https://bugs.launchpad.net/nova/+bug/1246201