anchor.diff:  
   internal_create_user(Mech, Creds, Name, Pass, Role, State) ->
       case user_exists(Name, State) of
  -	true -> {{error, user_exists}, State};
  +	true -> authorize_and_do(Mech, Creds, admin, fun(_,_) -> {error, user_exists} end, ignored, State);
   	_ -> authorize_and_do(Mech, Creds, admin, fun do_create_user/2, {Name, Pass, Role, []}, State)
       end.
   
  
positive.code:     
  internal_delete_user(Mech,Creds,Name,State) ->
      case user_exists(Name, State) of
  	false -> {{error, no_such_user}, State};
  	_ -> authorize_and_do(Mech, Creds, admin, fun do_delete_user/2, Name, State)
      end.
  
  
negative.code: 
  internal_modify_user(Mech,Creds,User,Options,State) ->
      case user_exists(User, State) of
  	false -> authorize_and_do(Mech, Creds, admin, fun(_,_) -> {error, no_such_user} end, ignored, State);
  	_ -> authorize_and_do(Mech, Creds, admin, fun do_modify_user/2, {User, Options}, State)
      end.
  
  