Fix unfilled format string in add_execution_profile timeout message

The error message at Cluster.add_execution_profile() had an unfilled %s
placeholder: 'Failed to create all new connection pools in the %ss timeout.'
The pool_wait_timeout value was never interpolated into the string, so
users would see a literal '%s' instead of the actual timeout value.

Signed-off-by: Yaniv Kaul <yaniv.kaul@scylladb.com>

Author: mykaul

cassandra/cluster.py

@@ -1683,7 +1683,7 @@ def add_execution_profile(self, name, profile, pool_wait_timeout=5):
             futures.update(session.update_created_pools())
         _, not_done = wait_futures(futures, pool_wait_timeout)
         if not_done:
-            raise OperationTimedOut("Failed to create all new connection pools in the %ss timeout.")
+            raise OperationTimedOut("Failed to create all new connection pools in the %ss timeout." % pool_wait_timeout)
 
     def connection_factory(self, endpoint, host_conn = None, *args, **kwargs):
         """