mercurial/ui.py

--- a/mercurial/ui.py	Wed May 27 10:44:04 2015 -0700
+++ b/mercurial/ui.py	Sun May 31 14:40:28 2015 +0900
@@ -867,6 +867,7 @@
                                ''.join(causetb),
                                ''.join(exconly))
             else:
+                self.flush()  # flush debug or status message
                 traceback.print_exception(exc[0], exc[1], exc[2],
                                           file=self.ferr)
         return self.tracebackflag or force