Patching better 412 error messages from mis-commit on old api06 branch.

diff --cc app/models/relation.rb
index 464d1646cdedbec5523624fbabba614e2c46855b,2032e677046684067287dddb14e0f7eddecf528c..8a211b84f0498888108754c4b2e1bc70032a906c
--- 1/app/models/relation.rb
--- 2/app/models/relation.rb
+++ b/app/models/relation.rb
@@@ -249,8 -249,8 +249,8 @@@ class Relation < ActiveRecord::Bas
  
    def update_from(new_relation, user)
      check_consistency(self, new_relation, user)
-     if !new_relation.preconditions_ok?
-       raise OSM::APIPreconditionFailedError.new
 -    unless preconditions_ok?
++    unless new_relation.preconditions_ok?
+       raise OSM::APIPreconditionFailedError.new("Cannot update relation #{self.id}: data or member data is invalid.")
      end
      self.changeset_id = new_relation.changeset_id
      self.changeset = new_relation.changeset

diff --cc app/models/way.rb
Simple merge