         else if response.statusCode is 304
           deferred.resolve "[row #{rowIndex}] Product update not necessary."
         else if response.statusCode is 400
-          humanReadable = JSON.stringify body, null, '  '
-          deferred.resolve "[row #{rowIndex}] Problem on updating product:\n" + humanReadable
+          deferred.resolve "[row #{rowIndex}] Problem on updating product:\n" + body
         else
-          humanReadable = JSON.stringify body, null, '  '
-          deferred.reject "[row #{rowIndex}] Error on updating product: " + humanReadable
+          deferred.reject "[row #{rowIndex}] Error on updating product: " + body
 
     deferred.promise
 

    deferred = Q.defer()
    allSameValueAttributes = types.id2SameForAllAttributes[product.productType.id]
    diff = @sync.buildActions(product, existingProduct, allSameValueAttributes)
    diff.update (error, response, body) =>
      @tickProgress()
      if error

          if ignore400
            deferred.resolve "[row #{rowIndex}] Product is already #{action}ed."
          else
            deferred.reject "[row #{rowIndex}] Problem on #{action}ing product:\n" + body
        else
          deferred.reject "[row #{rowIndex}] Problem on #{action}ing product (code #{response.statusCode}): " + body

    deferred.promise

