Deprecate Windows support

Because WinStackers project has been retired, running OpenStack on
Windows operating systems is no longer maintained.

Change-Id: Ic5971ee22aa309a8b46f21fccaa8be7c0091fb0c

os_vif/internal/ip/api.py

@@ -11,10 +11,13 @@
 #    under the License.
 
 import os
+import warnings
 
 from oslo_log import log as logging
 
 if os.name == 'nt':
+    warnings.warn('Support for Windows OS is deprecated.',
+                  category=DeprecationWarning, stacklevel=3)
     from os_vif.internal.ip.windows.impl_netifaces import \
         Netifaces as ip_lib_class
 else:

releasenotes/notes/deprecate-windows-support-49f5ca1b1a1f4d66.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - |
+    Support for Windows operating systems has been deprecated.