fix the compatiable problem between PY2 and PY3 (issue#20749) (#20942)

* fix the compatiable problem between PY2 and PY3.

* add ut, test=develop

* add proxy, test=develop

* download dataset before test, test=develop

python/paddle/dataset/sentiment.py

@@ -28,6 +28,9 @@ from itertools import chain
 
 import nltk
 from nltk.corpus import movie_reviews
+import ssl
+ssl._create_default_https_context = ssl._create_unverified_context
+from functools import cmp_to_key
 
 import paddle.dataset.common
 
@@ -68,7 +71,7 @@ def get_word_dict():
             for words in movie_reviews.words(field):
                 word_freq_dict[words] += 1
     words_sort_list = list(six.iteritems(word_freq_dict))
-    words_sort_list.sort(cmp=lambda a, b: b[1] - a[1])
+    words_sort_list.sort(key=cmp_to_key(lambda a, b: b[1] - a[1]))
     for index, word in enumerate(words_sort_list):
         words_freq_sorted.append((word[0], index))
     return words_freq_sorted

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

+#   Copyright (c) 2018 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""
+TestCases for Dataset,
+including create, config, run, etc.
+"""
+
+from __future__ import print_function
+import numpy as np
+import unittest
+import os
+import paddle
+import zipfile
+import paddle.dataset.common
+
+URL = "https://corpora.bj.bcebos.com/movie_reviews%2Fmovie_reviews.zip"
+MD5 = '155de2b77c6834dd8eea7cbe88e93acb'
+
+
+class TestDatasetSentiment(unittest.TestCase):
+    """  TestCases for Sentiment. """
+
+    def setUp(self):
+        paddle.dataset.common.download(
+            URL, 'corpora', md5sum=MD5, save_name='movie_reviews.zip')
+        path = os.path.join(paddle.dataset.common.DATA_HOME, 'corpora')
+        filename = os.path.join(path, 'movie_reviews.zip')
+        zip_file = zipfile.ZipFile(filename)
+        zip_file.extractall(path)
+        zip_file.close()
+
+    def test_get_word_dict(self):
+        """ Testcase for get_word_dict. """
+        words_freq_sorted = paddle.dataset.sentiment.get_word_dict()
+        print(words_freq_sorted)
+        self.assertTrue(len(words_freq_sorted) == 39768)
+
+
+if __name__ == '__main__':
+    unittest.main()