Fix transplant error message to correspond with test

hgext/transplant.py

@@ -363,7 +363,7 b' class transplanter(object):'
                 inmsg = True
                 message.append(line)
         if None in (user, date):
-            raise util.Abort(_("filter produced garbled log file"))
+            raise util.Abort(_("filter corrupted changeset (no user or date)"))
         return (node, user, date, '\n'.join(message), parents)
 
     def log(self, user, date, message, p1, p2, merge=False):

tests/test-transplant.t

@@ -374,7 +374,7 b' test transplant with filter handles inva'
   $ chmod +x test-filter-invalid-log
   $ hg transplant -s ../t --filter ./test-filter-invalid-log 0
   filtering * (glob)
-  abort: filter failed
+  abort: filter corrupted changeset (no user or date)
   [255]
 
 test with a win32ext like setup (differing EOLs)