Adds a 'labels' property to the container model

The Docker API seems to respond with a 'null' value for the 'Labels'
attribute from containers that were created with older Docker versions.
An empty dictionary is returned in this case.

Signed-off-by: Frank Sachsenheim <funkyfuture@riseup.net>

docker/models/containers.py

@@ -18,6 +18,14 @@ class Container(Model):
         if self.attrs.get('Name') is not None:
             return self.attrs['Name'].lstrip('/')
 
+    @property
+    def labels(self):
+        """
+        The labels of a container as dictionary.
+        """
+        result = self.attrs['Config'].get('Labels')
+        return result or {}
+
     @property
     def status(self):
         """

docs/containers.rst

@@ -25,6 +25,7 @@ Container objects
   .. autoattribute:: short_id
   .. autoattribute:: name
   .. autoattribute:: status
+  .. autoattribute:: labels
   .. py:attribute:: attrs
 
     The raw representation of this object from the server.

tests/unit/fake_api.py

@@ -134,7 +134,7 @@ def get_fake_inspect_container(tty=False):
     status_code = 200
     response = {
         'Id': FAKE_CONTAINER_ID,
-        'Config': {'Privileged': True, 'Tty': tty},
+        'Config': {'Labels': {'foo': 'bar'}, 'Privileged': True, 'Tty': tty},
         'ID': FAKE_CONTAINER_ID,
         'Image': 'busybox:latest',
         'Name': 'foobar',

tests/unit/models_containers_test.py

@@ -390,6 +390,11 @@ class ContainerTest(unittest.TestCase):
         container.kill(signal=5)
         client.api.kill.assert_called_with(FAKE_CONTAINER_ID, signal=5)
 
+    def test_labels(self):
+        client = make_fake_client()
+        container = client.containers.get(FAKE_CONTAINER_ID)
+        assert container.labels == {'foo': 'bar'}
+
     def test_logs(self):
         client = make_fake_client()
         container = client.containers.get(FAKE_CONTAINER_ID)