diff --git a/testing/tools/websocketprocessbridge/websocketprocessbridge_requirements_3.txt b/testing/tools/websocketprocessbridge/websocketprocessbridge_requirements_3.txt
--- a/testing/tools/websocketprocessbridge/websocketprocessbridge_requirements_3.txt
+++ b/testing/tools/websocketprocessbridge/websocketprocessbridge_requirements_3.txt
@@ -1,4 +1,5 @@
 # This file is the websocketprocess requirements.txt used with python 3.
+pyrsistent
 
 # needed by txws, and we'd like pip to get it from the local server before setuptools tries pypi
 six