templater: give slightly nicer error for unknown map entries

mercurial/templater.py

@@ -214,6 +214,8 b' class templater(object):'
         if not t in self.cache:
             try:
                 self.cache[t] = open(self.map[t][1]).read()
+            except KeyError, inst:
+                raise util.Abort(_('"%s" not in template map') % inst.args[0])
             except IOError, inst:
                 raise IOError(inst.args[0], _('template file %s: %s') %
                               (self.map[t][1], inst.args[1]))

tests/test-command-template.t

@@ -449,7 +449,7 b' Error if style missing key:'
 
   $ echo 'q = q' > t
   $ hg log --style ./t
-  abort: ./t: no key named 'changeset'
+  abort: "changeset" not in template map
   [255]
 
 Error if include fails: