Fix dataset url (#314)

torchvision/datasets/cifar.py

@@ -32,7 +32,7 @@ class CIFAR10(data.Dataset):
 
     """
     base_folder = 'cifar-10-batches-py'
-    url = "http://www.cs.toronto.edu/~kriz/cifar-10-python.tar.gz"
+    url = "https://www.cs.toronto.edu/~kriz/cifar-10-python.tar.gz"
     filename = "cifar-10-python.tar.gz"
     tgz_md5 = 'c58f30108f718f92721af3b95e74349a'
     train_list = [
@@ -162,7 +162,7 @@ class CIFAR10(data.Dataset):
 
 class CIFAR100(CIFAR10):
     base_folder = 'cifar-100-python'
-    url = "http://www.cs.toronto.edu/~kriz/cifar-100-python.tar.gz"
+    url = "https://www.cs.toronto.edu/~kriz/cifar-100-python.tar.gz"
     filename = "cifar-100-python.tar.gz"
     tgz_md5 = 'eb9058c3a382ffc7106e4002c42a8d85'
     train_list = [

torchvision/datasets/utils.py

@@ -36,5 +36,12 @@ def download_url(url, root, filename, md5):
     if os.path.isfile(fpath) and check_integrity(fpath, md5):
         print('Using downloaded and verified file: ' + fpath)
     else:
-        print('Downloading ' + url + ' to ' + fpath)
-        urllib.request.urlretrieve(url, fpath)
+        try:
+            print('Downloading ' + url + ' to ' + fpath)
+            urllib.request.urlretrieve(url, fpath)
+        except:
+            if url[:5] == 'https':
+                url = url.replace('https:', 'http:')
+                print('Failed download. Trying https -> http instead.'
+                      ' Downloading ' + url + ' to ' + fpath)
+                urllib.request.urlretrieve(url, fpath)