abort build on error

build.sh

@@ -1,5 +1,8 @@
 #!/bin/sh
 
+set -e
+set -x
+
 hugo $(cat .hugo-params)
 ./tools/merge_cals.py
 upcoming="$(tools/gen_upcoming.py static/all.ics 20 5 | tr '\n' ' ')"

flake.nix

@@ -30,6 +30,7 @@
                 python-pkgs.icalendar
                 python-pkgs.pytz
               ]))
+              shellcheck
             ];
           };
         }