Revert some exception type changes in revlog

mercurial/revlog.py

@@ -291,8 +291,8 b' class revlog:'
             for n in self.nodemap:
                 if hex(n).startswith(id):
                     c.append(n)
-            if len(c) > 1: raise RevlogError("Ambiguous identifier")
-            if len(c) < 1: raise RevlogError("No match found")
+            if len(c) > 1: raise KeyError("Ambiguous identifier")
+            if len(c) < 1: raise KeyError("No match found")
             return c[0]
 
         return None