Trying to add a docker repository with a length of more than 30 characters for the image name part fails with error: "Docker upstream name must be a valid docker name"

This seems somewhat arbitrary, image with a name of more than 30 characters do exist on Docker Hub (and other publicly accessible registries).

<pre>
$ sudo docker search openvswitch | grep -E "/[a-zA-Z0-9-]{30}[^ ]"
docker.io    docker.io/intelonp/centos-source-neutron-openvswitch-agent                            centos-source-neutron-openvswitch-agent         0                    [OK]
docker.io    docker.io/intelonp/centos-source-openvswitch-db-server                                centos-source-openvswitch-db-server             0                    [OK]
docker.io    docker.io/intelonp/centos-source-openvswitch-vswitchd                                 centos-source-openvswitch-vswitchd              0                    [OK]
docker.io    docker.io/rbbratta/centos-source-neutron-openvswitch-agent                            centos-source-neutron-openvswitch-agent         0                    [OK]
docker.io    docker.io/rbbratta/centos-source-openvswitch-db-server                                centos-source-openvswitch-db-server             0                    [OK]
docker.io    docker.io/rbbratta/centos-source-openvswitch-vswitchd                                 centos-source-openvswitch-vswitchd              0                    [OK]
docker.io    docker.io/tripleoupstream/centos-binary-openvswitch-vswitchd                                                                          0

</pre>