update multi_pass_reader unittest

Author: JiayiFeng

python/paddle/fluid/tests/unittests/test_multi_pass_reader.py

@@ -57,8 +57,12 @@ def test_main(self):
             exe.run(fluid.default_startup_program())
 
             batch_count = 0
-            while not data_file.eof():
-                img_val, = exe.run(fetch_list=[img])
+            while True:
+                try:
+                    img_val, = exe.run(fetch_list=[img])
+                except fluid.core.EnforceNotMet as ex:
+                    self.assertIn("There is no next data.", ex.message)
+                    break
                 batch_count += 1
                 self.assertLessEqual(img_val.shape[0], self.batch_size)
             data_file.reset()