Don't fall when just loading heatv1 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: I56871fec52e656d764e95ca2e93f10fe97d6a3c6
Related-Issue: https://mirantis.jira.com/browse/PROD-26920
diff --git a/_modules/heatv1/common.py b/_modules/heatv1/common.py
index 06eabff..3859ca7 100644
--- a/_modules/heatv1/common.py
+++ b/_modules/heatv1/common.py
@@ -2,7 +2,10 @@
 import six
 import uuid
 
-import os_client_config
+try:
+    import os_client_config
+except ImportError:
+    os_client_config = None
 from salt import exceptions
 
 
@@ -12,6 +15,10 @@
 
 
 def get_raw_client(cloud_name):
+    if not os_client_config:
+        raise exceptions.SaltInvocationError(
+            "Cannot load os-client-config. Please check your environment "
+            "configuration.")
     config = os_client_config.OpenStackConfig()
     cloud = config.get_one_cloud(cloud_name)
     adapter = cloud.get_session_client(SERVICE_KEY)
@@ -106,4 +113,4 @@
                 uuid = resp[0]['id']
             return func(uuid, *args[start_arg:], **kwargs)
         return wrapped_f
-    return wrap
\ No newline at end of file
+    return wrap