Protect push tests from environment

If the tests are run somewhere that somebody has push auth
configured, the auth headers bleed into the tests. Add a mock
to prevent that from happening.

Author: emonty

tests/test.py

@@ -49,6 +49,10 @@ def response(status_code=200, content='', headers=None, reason=None, elapsed=0,
     return res
 
 
+def fake_resolve_authconfig(authconfig, registry=None):
+    return None
+
+
 def fake_resp(url, data=None, **kwargs):
     status_code, content = fake_api.fake_responses[url]()
     return response(status_code=status_code, content=content)
@@ -1174,7 +1178,9 @@ def test_insert_image(self):
 
     def test_push_image(self):
         try:
-            self.client.push(fake_api.FAKE_IMAGE_NAME)
+            with mock.patch('docker.auth.auth.resolve_authconfig',
+                            fake_resolve_authconfig):
+                self.client.push(fake_api.FAKE_IMAGE_NAME)
         except Exception as e:
             self.fail('Command should not raise exception: {0}'.format(e))
 
@@ -1188,7 +1194,9 @@ def test_push_image(self):
 
     def test_push_image_stream(self):
         try:
-            self.client.push(fake_api.FAKE_IMAGE_NAME, stream=True)
+            with mock.patch('docker.auth.auth.resolve_authconfig',
+                            fake_resolve_authconfig):
+                self.client.push(fake_api.FAKE_IMAGE_NAME, stream=True)
         except Exception as e:
             self.fail('Command should not raise exception: {0}'.format(e))