Add a plugin not found handler

rowbot

@@ -92,6 +92,7 @@ run_callbacks() {
   shift
 
   while IFS= read -r; do
+    log_info "running callback %s" "$REPLY"
     "$REPLY" "$@"
     (( status |= $? ))
   done < <(compgen -A function "$filter")
@@ -767,6 +768,8 @@ plugin_run() {
     for plugin in "${plugins[@]}"; do
       "$plugin" "$@"
     done
+  else
+    run_callbacks plugin_not_found_
   fi
 }