Fix.

diff --git a/trixie/copy/desktop/home/plom/.plomlib/abort_if_command_unknown.sh b/trixie/copy/desktop/home/plom/.plomlib/abort_if_command_unknown.sh
new file mode 120000 (symlink)
index 0000000..74ec9ca
--- /dev/null
+++ b/trixie/copy/desktop/home/plom/.plomlib/abort_if_command_unknown.sh
@@ -0,0 +1 @@
+../../../../../scripts/lib/abort_if_command_unknown.sh
\ No newline at end of file