Reverted Jinja2 library back to version 2.10.3 due to the bug.

This bug was introduced in version 2.11.0 and is fixed in 2.11.2, which is not yet released. Reference:

	https://github.com/pallets/jinja/issues/1145

conf/requirements.pip

@@ -6,7 +6,7 @@ babel==2.8.0
 wtforms==2.2.1
 sqlalchemy==1.3.15
 alembic==1.4.2
-jinja2==2.11.1
+jinja2==2.10.3
 blinker==1.4
 bsddb3==6.2.7
 flask==1.1.1