Added utils.ping and used to expand registry URL (http VS https)

docker/auth.py

@@ -18,6 +18,8 @@ import os
 
 import six
 
+import utils
+
 INDEX_URL = 'https://index.docker.io/v1/'
 
 def swap_protocol(url):
@@ -33,7 +35,8 @@ def expand_registry_url(hostname):
         if '/' not in hostname[9:]:
             hostname = hostname + '/v1/'
         return hostname
-    #FIXME: ping https then fallback to http
+    if utils.ping('https://' + hostname + '_ping'):
+        return 'https://' + hostname + '/v1/'
     return 'http://' + hostname + '/v1/'
 
 

docker/utils.py

@@ -12,10 +12,12 @@
 #    See the License for the specific language governing permissions and
 #    limitations under the License.
 
-import six
 import tarfile
 import tempfile
 
+import requests
+import six
+
 if six.PY3:
     from io import StringIO
 else:
@@ -44,5 +46,14 @@ def tar(self, path):
     f.seek(0)
     return f
 
+
 def compare_version(v1, v2):
-    return float(v2) - float(v1)
\ No newline at end of file
+    return float(v2) - float(v1)
+
+
+def ping(url):
+    try:
+        res = requests.get(url)
+        return res.status >= 400
+    except Exception:
+        return False