In the configuration of nginx, there is the following comment:
include conf.d/tuleap.d/*.conf;
# Available here in case of emergency, uncomment the
# line below (and comment the line above)
#include conf.d/tuleap-apache.proxy;
Unfortunately, when we activate the emergency, nginx is not happy because it does not find tuleap-apache.proxy file. It seems that this file is not packaged or deployed.