anchor.diff:  
   
   api_result(ReqData, Context, Result) ->
  -    case Result of 
  +    case Result of
           {error, Err=missing_arg, Arg} ->
               api_error(400, Err, "Missing argument: " ++ Arg, ReqData, Context);
   
  
positive.code: %% Licensed under the Apache License, Version 2.0 (the "License");
  %% you may not use this file except in compliance with the License.
  %% You may obtain a copy of the License at
  %% 
  %%     http://www.apache.org/licenses/LICENSE-2.0
  %% 
  %% Unless required by applicable law or agreed to in writing, software
  %% distributed under the License is distributed on an "AS IS" BASIS,
  %% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  
negative.code: 
  
  process_post(ReqData, Context) ->
      Module = z_context:get("module", Context),
      case Module:process_post(ReqData, Context) of
          ok ->
              {true, ReqData, Context};
          Result ->
              api_result(ReqData, Context, Result)
      end.
  