add .tgz support to extract_archive (#1650)

* tgz updates

* tgz updates

* tgz updates

test/test_datasets_utils.py

@@ -86,7 +86,7 @@ class Tester(unittest.TestCase):
 
     @unittest.skipIf('win' in sys.platform, 'temporarily disabled on Windows')
     def test_extract_tar(self):
-        for ext, mode in zip(['.tar', '.tar.gz'], ['w', 'w:gz']):
+        for ext, mode in zip(['.tar', '.tar.gz', '.tgz'], ['w', 'w:gz', 'w:gz']):
             with get_tmp_dir() as temp_dir:
                 with tempfile.NamedTemporaryFile() as bf:
                     bf.write("this is the content".encode())

torchvision/datasets/utils.py

@@ -213,6 +213,10 @@ def _is_targz(filename):
     return filename.endswith(".tar.gz")
 
 
+def _is_tgz(filename):
+    return filename.endswith(".tgz")
+
+
 def _is_gzip(filename):
     return filename.endswith(".gz") and not filename.endswith(".tar.gz")
 
@@ -228,7 +232,7 @@ def extract_archive(from_path, to_path=None, remove_finished=False):
     if _is_tar(from_path):
         with tarfile.open(from_path, 'r') as tar:
             tar.extractall(path=to_path)
-    elif _is_targz(from_path):
+    elif _is_targz(from_path) or _is_tgz(from_path):
         with tarfile.open(from_path, 'r:gz') as tar:
             tar.extractall(path=to_path)
     elif _is_tarxz(from_path) and PY3: