add detail error to dataset

ppocr/data/simple_dataset.py

@@ -14,6 +14,7 @@
 import numpy as np
 import os
 import random
+import traceback
 from paddle.io import Dataset
 
 from .imaug import transform, create_operators
@@ -117,9 +118,10 @@ class SimpleDataSet(Dataset):
             data['ext_data'] = self.get_ext_data()
             outs = transform(data, self.ops)
         except Exception as e:
+            error_meg = traceback.format_exc()
             self.logger.error(
                 "When parsing line {}, error happened with msg: {}".format(
-                    data_line, e))
+                    data_line, error_meg))
             outs = None
         if outs is None:
             # during evaluation, we should fix the idx to get same results for many times of evaluation.