Define IpAddressAlreadyAllocated exception

This exception will raise when creating a port with an IP allocated
IP address. This exception needs to be defined in client so that
nova can catch it and perform the error handling.

Needed-By: I5bee9ae18764b6f285ecc5e8d7148a1019c74701
Change-Id: Ie1d4581d334e1ec491e56371c62978945ae24a44
Related-Bug: #1744103

neutronclient/common/exceptions.py

@@ -162,6 +162,10 @@ class IpAddressInUseClient(Conflict):
     pass
 
 
+class IpAddressAlreadyAllocatedClient(Conflict):
+    pass
+
+
 class InvalidIpForNetworkClient(BadRequest):
     pass
 

neutronclient/tests/unit/test_cli20.py

@@ -911,6 +911,8 @@ class CLITestV20ExceptionHandler(CLITestV20Base):
             ('OverQuota', exceptions.OverQuotaClient, 409),
             ('InvalidIpForNetwork', exceptions.InvalidIpForNetworkClient, 400),
             ('InvalidIpForSubnet', exceptions.InvalidIpForSubnetClient, 400),
+            ('IpAddressAlreadyAllocated',
+             exceptions.IpAddressAlreadyAllocatedClient, 400),
         ]
 
         error_msg = 'dummy exception message'

releasenotes/notes/Define-IpAddressAlreadyAllocatedClient-exception-e8600ca5ba1c7f45.yaml

@@ -0,0 +1,6 @@
+---
+other:
+  - |
+    Define a new exception type ``IpAddressAlreadyAllocatedClient``.
+    Users can catch this specific exception instead of the generic
+    ``NeutronClientException``.