Jinja 2.9.x breaks password generation in cookiecutter templates

Change-Id: I3269ea465e109f401566ce5976d9aad210f73c87
diff --git a/requirements.txt b/requirements.txt
index 7a09d68..18aad90 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,3 +2,4 @@
 PyYAML>=3.1.0
 six>=1.9.0
 cookiecutter
+jinja2==2.8.1