Update install-everything-on-ubuntu-16.04.sh

due warning

opt.d/install-everything-on-ubuntu-16.04.sh

@@ -28,4 +28,11 @@ sudo pip install onionbalance || exit 1
 sudo find /usr/local/bin /usr/local/lib -perm -0400 -print0 | sudo xargs -0 chmod a+r || exit 1
 sudo find /usr/local/bin /usr/local/lib -perm -0100 -print0 | sudo xargs -0 chmod a+x || exit 1
 
+echo ""
+echo IMPORTANT: some versions of Ubuntu packages are unfortunately old. 
+echo Because of this, when starting projects you may see messages like: 
+echo ">" could not open error log file: open /var/log/nginx/error.log failed
+echo ...and these specific messages may be safely ignored.
+echo done.
+
 exit 0