command-not-found: Simplify the wrappers

- Now we check for database existence in the script.
- Nix ensures the script exists.
- The 126 error code check and retry is leftover from an old version.

nixos/modules/programs/command-not-found/command-not-found.nix

@@ -54,44 +54,14 @@ in
 
   config = lib.mkIf cfg.enable {
     programs.bash.interactiveShellInit = ''
-      # This function is called whenever a command is not found.
       command_not_found_handle() {
-        local p='${commandNotFound}/bin/command-not-found'
-        if [ -x "$p" ] && [ -f '${cfg.dbPath}' ]; then
-          # Run the helper program.
-          "$p" "$@"
-          # Retry the command if we just installed it.
-          if [ $? = 126 ]; then
-            "$@"
-          else
-            return 127
-          fi
-        else
-          echo "$1: command not found" >&2
-          return 127
-        fi
+        '${commandNotFound}/bin/command-not-found' "$@"
       }
     '';
 
     programs.zsh.interactiveShellInit = ''
-      # This function is called whenever a command is not found.
       command_not_found_handler() {
-        local p='${commandNotFound}/bin/command-not-found'
-        if [ -x "$p" ] && [ -f '${cfg.dbPath}' ]; then
-          # Run the helper program.
-          "$p" "$@"
-
-          # Retry the command if we just installed it.
-          if [ $? = 126 ]; then
-            "$@"
-          else
-            return 127
-          fi
-        else
-          # Indicate than there was an error so ZSH falls back to its default handler
-          echo "$1: command not found" >&2
-          return 127
-        fi
+        '${commandNotFound}/bin/command-not-found' "$@"
       }
     '';