diff -r 7d4ce4b567c5 -r 177742666abd mercurial/filemerge.py
--- a/mercurial/filemerge.py	Sat May 13 03:28:36 2017 +0900
+++ b/mercurial/filemerge.py	Sat May 13 03:28:36 2017 +0900
@@ -133,7 +133,7 @@
     def check(tool, pat, symlink, binary, changedelete):
         tmsg = tool
         if pat:
-            tmsg += " specified for " + pat
+            tmsg = _("%s (for pattern %s)") % (tool, pat)
         if not _findtool(ui, tool):
             if pat: # explicitly requested tool deserves a warning
                 ui.warn(_("couldn't find merge tool %s\n") % tmsg)