Fix [H405] pep rule in heat_integrationtests

Implements bp docstring-improvements

Change-Id: I7aebbdafef121c3414e6a0260452c1353af62e88
diff --git a/common/exceptions.py b/common/exceptions.py
index 5132850..b092fd0 100644
--- a/common/exceptions.py
+++ b/common/exceptions.py
@@ -12,8 +12,7 @@
 
 
 class IntegrationException(Exception):
-    """
-    Base Tempest Exception
+    """Base Tempest Exception.
 
     To correctly use this class, inherit from it and define
     a 'message' property. That message will get printf'd