Fix pulling images with stream=True

Pulling an image with option `stream=True` like this:
```
client.api.pull('docker.io/user/repo_name', tag='latest', stream=True)
```
without consuming the generator oftentimes results in premature drop of the connection. Docker daemon tries to send progress of pulling the image to the client, but it encounters an error (broken pipe) and therefore cancells the pull action:
```
Thread 1 "dockerd-dev" received signal SIGPIPE, Broken pipe.
ERRO[2018-09-03T05:12:35.746497638+02:00] Not continuing with pull after error: context canceled
```
As described in issue #2116, even though client receives response with status code 200, image is not pulled.

Closes #2116

Signed-off-by: Przemysław Adamek <[email protected]>

Author: adw1n

docker/api/image.py

@@ -334,7 +334,8 @@ def pull(self, repository, tag=None, stream=False, auth_config=None,
         Args:
             repository (str): The repository to pull
             tag (str): The tag to pull
-            stream (bool): Stream the output as a generator
+            stream (bool): Stream the output as a generator. Make sure to
+                consume the generator, otherwise pull might get cancelled.
             auth_config (dict): Override the credentials that
                 :py:meth:`~docker.api.daemon.DaemonApiMixin.login` has set for
                 this request. ``auth_config`` should contain the ``username``

docker/models/images.py

@@ -425,6 +425,7 @@ def pull(self, repository, tag=None, **kwargs):
         if not tag:
             repository, tag = parse_repository_tag(repository)
 
+        kwargs['stream'] = False
         self.client.api.pull(repository, tag=tag, **kwargs)
         if tag:
             return self.get('{0}{2}{1}'.format(

tests/unit/models_containers_test.py

@@ -232,7 +232,8 @@ def test_run_pull(self):
         container = client.containers.run('alpine', 'sleep 300', detach=True)
 
         assert container.id == FAKE_CONTAINER_ID
-        client.api.pull.assert_called_with('alpine', platform=None, tag=None)
+        client.api.pull.assert_called_with('alpine', platform=None, tag=None,
+                                           stream=False)
 
     def test_run_with_error(self):
         client = make_fake_client()

tests/unit/models_images_test.py

@@ -43,15 +43,17 @@ def test_load(self):
     def test_pull(self):
         client = make_fake_client()
         image = client.images.pull('test_image:latest')
-        client.api.pull.assert_called_with('test_image', tag='latest')
+        client.api.pull.assert_called_with('test_image', tag='latest',
+                                           stream=False)
         client.api.inspect_image.assert_called_with('test_image:latest')
         assert isinstance(image, Image)
         assert image.id == FAKE_IMAGE_ID
 
     def test_pull_multiple(self):
         client = make_fake_client()
         images = client.images.pull('test_image')
-        client.api.pull.assert_called_with('test_image', tag=None)
+        client.api.pull.assert_called_with('test_image', tag=None,
+                                           stream=False)
         client.api.images.assert_called_with(
             all=False, name='test_image', filters=None
         )