format_paragraph_event wasn't returning 'break'

Lib/idlelib/FormatParagraph.py

@@ -75,6 +75,7 @@ class FormatParagraph:
         else:
             text.mark_set("insert", last)
         text.see("insert")
+        return "break"
 
 def find_paragraph(text, mark):
     lineno, col = map(int, mark.split("."))