Fix trailing whitespace in keyword.py (GH-20881)

Author: pablogsal

Tools/peg_generator/pegen/keywordgen.py

@@ -67,8 +67,8 @@ def main():
         all_keywords = sorted(list(gen.callmakervisitor.keyword_cache.keys()) + EXTRA_KEYWORDS)
         all_soft_keywords = sorted(gen.callmakervisitor.soft_keywords)
 
-        keywords = "    " + ",\n    ".join(map(repr, all_keywords))
-        soft_keywords = "    " + ",\n    ".join(map(repr, all_soft_keywords))
+        keywords = "" if not all_keywords else "    " + ",\n    ".join(map(repr, all_keywords))
+        soft_keywords = "" if not all_soft_keywords else "    " + ",\n    ".join(map(repr, all_soft_keywords))
         thefile.write(TEMPLATE.format(keywords=keywords, soft_keywords=soft_keywords))