Gets can, cannot and must rules from github license API

def get_rules(license):
  """Gets can, cannot and must rules from github license API"""

  can = []
  cannot = []
  must = []
  req = requests.get("{base_url}/licenses/{license}".format(
                     base_url=BASE_URL, license=license), headers=_HEADERS)

  if req.status_code == requests.codes.ok:
    data = req.json()
    can = data["permitted"]
    cannot = data["forbidden"]
    must = data["required"]

  return can, cannot, must