checks for nonexistent dirs

tgbot/kollagen-bot/main.py

@@ -121,9 +121,13 @@ class KollagenBot:
             return False
 
         directories = [
-            os.path.join(self.base_dir or "./", dir) for dir in args.directories
+            (dir, os.path.join(self.base_dir or "./", dir)) for dir in args.directories
         ]
 
+        for orig_dir, full_path in directories:
+            if not os.path.exists(full_path):
+                raise FileNotFoundError(f'"{orig_dir}" does not exist.')
+
         mode = ["-m", args.mode] if args.mode else []
         num_images = ["-n", str(args.num_images)] if args.num_images else []
 
@@ -131,7 +135,7 @@ class KollagenBot:
             shell_cmd_line = [
                 self.kollagen_path,
                 "-r",
-                *directories,
+                *[full_path for _, full_path in directories],
                 "-w",
                 str(args.width),
                 "-h",