add more traceback to py_reader error msg, test=develop (#18722)

AUTHORS.md

@@ -46,6 +46,7 @@
 | reyoung | Yang Yu |
 | Sand3r- | Michal Gallus |
 | sfraczek | Sylwester Fraczek |
+| sneaxiy | Jin-Le Zeng |
 | Superjom | Chun-Wei Yan |
 | tensor-tang | Jian Tang |
 | tianbingsz | Tian-Bing Xu |

python/paddle/fluid/layers/io.py

@@ -17,6 +17,7 @@ from ..wrapped_decorator import signature_safe_contextmanager
 import multiprocessing
 import os
 import six
+import sys
 import threading
 
 from ..data_feeder import DataFeeder
@@ -595,7 +596,7 @@ def _py_reader(capacity,
             except Exception as ex:
                 feed_queue.close()
                 logging.warn('Your decorated reader has raised an exception!')
-                raise ex
+                six.reraise(*sys.exc_info())
 
         reader.thread = threading.Thread(target=__provider_thread__)
         reader.thread.daemon = True

python/paddle/fluid/reader.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 from . import core, dygraph
+import sys
 import six
 import warnings
 import numpy as np
@@ -443,7 +444,7 @@ class PyReader(object):
             except Exception as ex:
                 self._queue.close()
                 logging.warn('Your decorated reader has raised an exception!')
-                raise ex
+                six.reraise(*sys.exc_info())
 
         self._thread = threading.Thread(target=__thread_main__)
         self._thread.daemon = True