gguf-py : display the invalid gguf type (#13687)

Signed-off-by: Emmanuel Ferdman <emmanuelferdman@gmail.com>

gguf-py/gguf/gguf_reader.py

@@ -251,7 +251,7 @@ class GGUFReader:
                 offs += curr_size
             return offs - orig_offs, aparts, data_idxs, types
         # We can't deal with this one.
-        raise ValueError('Unknown/unhandled field type {gtype}')
+        raise ValueError(f'Unknown/unhandled field type {gtype}')
 
     def _get_tensor_info_field(self, orig_offs: int) -> ReaderField:
         offs = orig_offs