network_test.py leaks networks, eventually creating overlapping subnet

[bboreham]

Because test_create_check_duplicate does not add its network to tmp_networks, it does not get removed. After you do this 9 times, the subnet of the last one clashes with the hard-coded subnet of some other tests.

Symptoms:

~/.../github.com/docker/docker-py$ docker run --env="DOCKER_HOST=tcp://docker:2375" --link=dpy-dind:docker docker-py py.test tests/integration/network_test.py
============================= test session starts ==============================
platform linux2 -- Python 2.7.11 -- py-1.4.31 -- pytest-2.7.2
rootdir: /home/docker-py, inifile: pytest.ini
plugins: cov
collected 14 items

tests/integration/network_test.py ........F.....

=================================== FAILURES ===================================
______________ TestNetworks.test_create_network_with_ipam_config _______________
tests/integration/network_test.py:60: in test_create_network_with_ipam_config
    "c": "172.28.1.7",
tests/integration/network_test.py:15: in create_network
    net_id = self.client.create_network(net_name, *args, **kwargs)['Id']
docker/utils/decorators.py:35: in wrapper
    return f(self, *args, **kwargs)
docker/api/network.py:38: in create_network
    return self._result(res, json=True)
docker/client.py:158: in _result
    self._raise_for_status(response)
docker/client.py:154: in _raise_for_status
    raise errors.APIError(e, response, explanation=explanation)
E   APIError: 409 Client Error: Conflict ("cannot create network br-dc61b1db8337 (7b2f21e55a56fb4154dd19bebb45c8df037a09678c4a6bccdab3c16b8bf07a7f): conflicts with network dc61b1db833763e703457496bb3217406aeedf3afe8fd750ee21aba11a9f9a59 (br-dc61b1db8337): networks have overlapping IPv4")
===================== 1 failed, 13 passed in 7.76 seconds ======================

Here is the overlapping network:

$ docker network inspect dc61b1db833763e703457496bb3217406aeedf3afe8fd750ee21aba11a9f9a59
[
    {
        "Name": "dockerpy226972",
        "Id": "dc61b1db833763e703457496bb3217406aeedf3afe8fd750ee21aba11a9f9a59",
        "Scope": "local",
        "Driver": "bridge",
        "IPAM": {
            "Driver": "default",
            "Config": [
                {
                    "Subnet": "172.28.0.0/16",
                    "Gateway": "172.28.0.1/16"
                }
            ]
        },
        "Containers": {},
        "Options": {}
    }
]

Here we can see that running the test many times has created lots of them:

$ docker network ls
NETWORK ID          NAME                DRIVER
5e0177f6c3f2        dockerpy141491      bridge              
950801e0a554        dockerpy671862      bridge              
0f597023e885        dockerpy996320      bridge              
5a4b36f1e4d9        dockerpy140252      bridge              
dc61b1db8337        dockerpy226972      bridge              
be7192368018        dockerpy908156      bridge              
cf27cf9007ef        none                null                
426bcd88339a        host                host                
601318eb5c9b        bridge              bridge              
2f30a9567069        dockerpy163039      bridge              
023125dd8627        dockerpy744708      bridge              
af00edb1498a        dockerpy158611      bridge              

docker-py version: master
docker version: 1.10.3
python version: 2.7.6