Add deprecation warning in MNIST train[test]_labels[data] (#742)

torchvision/datasets/mnist.py

 from __future__ import print_function
+import warnings
 import torch.utils.data as data
 from PIL import Image
 import os
@@ -37,6 +38,26 @@ class MNIST(data.Dataset):
     classes = ['0 - zero', '1 - one', '2 - two', '3 - three', '4 - four',
                '5 - five', '6 - six', '7 - seven', '8 - eight', '9 - nine']
 
+    @property
+    def train_labels(self):
+        warnings.warn("train_labels has been renamed targets")
+        return self.targets
+
+    @property
+    def test_labels(self):
+        warnings.warn("test_labels has been renamed targets")
+        return self.targets
+
+    @property
+    def train_data(self):
+        warnings.warn("train_data has been renamed data")
+        return self.data
+
+    @property
+    def test_data(self):
+        warnings.warn("test_data has been renamed data")
+        return self.data
+
     def __init__(self, root, train=True, transform=None, target_transform=None, download=False):
         self.root = os.path.expanduser(root)
         self.transform = transform