Fix dataset resource warning (#26566)

* fix resource warning. test=develop

python/paddle/incubate/hapi/datasets/voc2012.py

@@ -27,7 +27,7 @@ __all__ = ["VOC2012"]
 VOC_URL = 'http://host.robots.ox.ac.uk/pascal/VOC/voc2012/\
 VOCtrainval_11-May-2012.tar'
 
-VOC_MD5 = '131da710f39b47a43fdfa256cbc11976'
+VOC_MD5 = '6cd6e144f989b92b3379bac3b3de84fd'
 SET_FILE = 'VOCdevkit/VOC2012/ImageSets/Segmentation/{}.txt'
 DATA_FILE = 'VOCdevkit/VOC2012/JPEGImages/{}.jpg'
 LABEL_FILE = 'VOCdevkit/VOC2012/SegmentationClass/{}.png'
@@ -131,3 +131,7 @@ class VOC2012(Dataset):
 
     def __len__(self):
         return len(self.data)
+
+    def __del__(self):
+        if self.data_tar:
+            self.data_tar.close()

python/paddle/incubate/hapi/datasets/wmt16.py

@@ -139,8 +139,11 @@ class WMT16(Dataset):
     def _load_dict(self, lang, dict_size, reverse=False):
         dict_path = os.path.join(paddle.dataset.common.DATA_HOME,
                                  "wmt16/%s_%d.dict" % (lang, dict_size))
-        if not os.path.exists(dict_path) or (
-                len(open(dict_path, "rb").readlines()) != dict_size):
+        dict_found = False
+        if os.path.exists(dict_path):
+            with open(dict_path, "rb") as d:
+                dict_found = len(d.readlines()) == dict_size
+        if not dict_found:
             self._build_dict(dict_path, dict_size, lang)
 
         word_dict = {}