Add warning for using the python bindings

The deprecation of python-neutronclient bindings
was discussed on the 2025.2 (Flamingo) PTG:
https://etherpad.opendev.org/p/apr2025-ptg-neutron#L163

Change-Id: Ieb08fc0884d7f386dc94090dce9d284d786d1ec2

README.rst

@@ -20,6 +20,7 @@ provides a Python API (the ``neutronclient`` module).
 .. note:: This project has been deprecated. The CLI code has been deleted
    and is not accessible anymore. The Python bindings are still in use by
    other projects but no new features will be added to this project.
+   All projects under Openstack governance migrating to use OpenstackSDK.
    Any new feature should be proposed to OpenStack SDK and OpenStack
    Client.
 

neutronclient/v2_0/client.py

@@ -250,6 +250,9 @@ class ClientBase(object):
     def __init__(self, **kwargs):
         """Initialize a new client for the Neutron v2.0 API."""
         super(ClientBase, self).__init__()
+        _logger.warning("The python binding code in neutronclient is "
+                        "deprecated in favor of OpenstackSDK, please use "
+                        "that as this will be removed in a future release.")
         self.retries = kwargs.pop('retries', 0)
         self.raise_errors = kwargs.pop('raise_errors', True)
         self.httpclient = client.construct_http_client(**kwargs)