Don't fall when just loading neutronv2 modules

this avoids loading warnings on salt-master that may not have
os-client-config installed, as salt tries to load them irrespective of
__virtual__() result.

Change-Id: I6d1a15c1dbdf0d95efb57e5aa41bae3d4b0eb7bf
Related-Issue: https://mirantis.jira.com/browse/PROD-27276
diff --git a/_modules/neutronv2/common.py b/_modules/neutronv2/common.py
index 699c6d9..88c08b6 100644
--- a/_modules/neutronv2/common.py
+++ b/_modules/neutronv2/common.py
@@ -1,9 +1,13 @@
 import functools
 import logging
-import os_client_config
 import time
 
-from salt.exceptions import CommandExecutionError
+try:
+    import os_client_config
+except ImportError:
+    os_client_config = None
+from salt import exceptions
+
 
 log = logging.getLogger(__name__)
 
@@ -49,6 +53,10 @@
 
 
 def _get_raw_client(cloud_name):
+    if not os_client_config:
+        raise exceptions.SaltInvocationError(
+            "Cannot load os-client-config. Please check your environment "
+            "configuration.")
     service_type = 'network'
     config = os_client_config.OpenStackConfig()
     cloud = config.get_one_cloud(cloud_name)
@@ -130,7 +138,7 @@
         break
     if not response or not response.content:
         if e:
-            raise CommandExecutionError(e)
+            raise exceptions.CommandExecutionError(e)
         else:
             return {}
     try: