Add many missing spaces in adjacent strings (#26751)

Add missing spaces in adjacent strings

examples/research_projects/performer/run_mlm_performer.py

@@ -466,7 +466,7 @@ if __name__ == "__main__":
         and not training_args.overwrite_output_dir
     ):
         raise ValueError(
-            f"Output directory ({training_args.output_dir}) already exists and is not empty."
+            f"Output directory ({training_args.output_dir}) already exists and is not empty. "
             "Use --overwrite_output_dir to overcome."
         )
 
@@ -558,7 +558,7 @@ if __name__ == "__main__":
         )
     else:
         raise ValueError(
-            "You are instantiating a new tokenizer from scratch. This is not supported by this script."
+            "You are instantiating a new tokenizer from scratch. This is not supported by this script. "
             "You can do it from another script, save it, and load it from here, using --tokenizer_name."
         )