text must be string, not list

master.cfg

@@ -107,15 +107,15 @@ def MessageGDBTesters (mode, name, build, results, master_status):
 send to the gdb-testers mailing list."""
     ss_list = build.getSourceStamps ()
     subj = "Failures on %s" % name
-    text = list ()
+    text = ""
     parser = DejaResults ()
-    text.append ("Commit(s) tested:\n")
+    text += ("Commit(s) tested:\n")
     for ss in ss_list:
-        text.append ("\t%s\n" % ss.revision)
-    text.append ("\n")
+        text += ("\t%s\n" % ss.revision)
+    text += ("\n")
     for log in build.getLogs ():
         if log.getName () == 'regressions' and log.hasContents ():
-            text.append (log.getText ())
+            text += log.getText ()
             break
     return { 'body' : text,
              'type' : 'plain',