Add Jinja2 to requirements

requirements.txt

@@ -15,6 +15,7 @@ ipyparallel == 6.2.4
 ipykernel == 5.1.4
 ipython == 7.12.0
 ipython_genutils == 0.2.0
+Jinja2 == 2.11.2
 jupyter == 1.0.0
 jupyter_client == 5.3.4
 jupyter_console == 6.1.0