templater: drop deprecated handling of KeyError from changeset_templater

It's been superseded by 09cde75e0613 and the previous patch. templater.mapfile
is no longer used and removed.

mercurial/cmdutil.py

@@ -1532,7 +1532,6 b' class changeset_templater(changeset_prin'
         props['revcache'] = {'copies': copies}
         props['cache'] = self.cache
 
-        try:
             # write header
             if self._parts['header']:
                 h = templater.stringify(self.t(self._parts['header'], **props))
@@ -1552,9 +1551,6 b' class changeset_templater(changeset_prin'
                 if not self.footer:
                     self.footer = templater.stringify(
                         self.t(self._parts['footer'], **props))
-        except KeyError as inst:
-            msg = _("%s: no key named '%s'")
-            raise error.Abort(msg % (self.t.mapfile, inst.args[0]))
 
 def gettemplate(ui, tmpl, style):
     """

mercurial/templater.py

@@ -956,7 +956,6 b' class templater(object):'
             defaults = {}
         if cache is None:
             cache = {}
-        self.mapfile = mapfile or 'template'
         self.cache = cache.copy()
         self.map = {}
         if mapfile: