curl \
  -k \
  -s \
  -X PATCH \
  -H "Content-Type:application/json" \
  -H "Accept: application/json" \
  -d '{"Description": "bar people"}' \
  --user caadmin:Secret.123 \
  https://localhost.localdomain:8443/ca/rest/admin/groups/foo-group | python -m json.tool
{
    "id": "foo-group",
    "GroupID": "foo-group",
    "Description": "bar people",
    "Link": {
        "rel": "self",
        "href": "https://localhost.localdomain:8443/ca/rest/admin/groups/foo-group",
        "type": "application/xml"
    }
}