Update util.py

Author: BobTheBuidler

mypyc/irbuild/util.py

@@ -143,7 +143,8 @@ def set_mypyc_attr(key: str, value: Any, line: int) -> None:
             lines[key] = line
         else:
             errors.error(f'"{key}" is not a supported "mypyc_attr"', path, line)
-            errors.note(f"supported keys: {'", "'.join(sorted(MYPYC_ATTRS))}", path, line)
+            supported_keys = ','.join(f'"{key}"' for key in sorted(MYPYC_ATTRS))
+            errors.note(f"supported keys: {supported_keys}", path, line)
 
     for dec in stmt.decorators:
         if d := get_mypyc_attr_call(dec):