templater: add try-except stub to runmember()

New wrapped interface will raise ParseError if the underlying object doesn't
support dict-like lookup operation.

mercurial/templateutil.py

@@ -666,9 +666,11 b' def runmember(context, mapping, data):'
     if util.safehasattr(d, 'tomap'):
         lm = context.overlaymap(mapping, d.tomap())
         return runsymbol(context, lm, memb)
+    try:
     if util.safehasattr(d, 'get'):
         return getdictitem(d, memb)
-
+        raise error.ParseError
+    except error.ParseError:
     sym = findsymbolicname(darg)
     if sym:
         raise error.ParseError(_("keyword '%s' has no member") % sym)