Fixup variable interpolation in test fixture error

Author: dpkp

test/fixtures.py

@@ -546,7 +546,7 @@ def _failure(error):
                     break
                 self._client.poll(timeout_ms=100)
             else:
-                raise RuntimeError('Could not connect to broker with node id %d' % (node_id,))
+                raise RuntimeError('Could not connect to broker with node id %s' % (node_id,))
 
             try:
                 future = self._client.send(node_id, request)