Convert a pile of obvious "yes/no" functions to return bool.
diff --git a/Lib/mailbox.py b/Lib/mailbox.py
index ed83489..853949b 100755
--- a/Lib/mailbox.py
+++ b/Lib/mailbox.py
@@ -151,7 +151,7 @@
         return self._regexp.match(line)
 
     def _portable_isrealfromline(self, line):
-        return 1
+        return True
 
     _isrealfromline = _strict_isrealfromline