Something changed with yangtools that made provider-named-selector ... contract to list enforced

Yangtools changed around mid-late march so that lists enforced strict, so DevStack integration breaks with EPG

ie
{
"endpoint-group": {
"id": "aaae3a2b-1b78-4efb-b312-c0489cf8e92e",
"name": "web",
"network-domain": "41957783-2cb5-441e-a468-c33d4a5a4ecd",
"provider-named-selector":

{ "contract": ["13ac8c16-2051-30cd-9920-b1e6b6ea5ae5"], "name": "Contract-13ac8c16-2051-30cd-9920-b1e6b6ea5ae5" }

}
}

See contract.