记录采购平均值计算，产生的详细日志

AutoTurnOver.Services/PurchaseAverageTargetServices.cs

@@ -189,7 +189,7 @@ namespace AutoTurnOver.Services
             }
             catch (Exception ex)
             {
-                task_log.ErrorMsg = ex.Message;
+                task_log.ErrorMsg = ex.Message + "--------" + ex.StackTrace;
             }
 
             conn.Update(task_log);