docs: def validate(self, nonce):
          """Does the nonce exist and is it valid for the request?"""
          if self.debug: print("Checking nonce " + str(nonce),file=sys.stderr)
          try:
              opaque, ip, expiretime = self.get(nonce) #pylint: disable=unused-variable
              if expiretime < time.time():
                  if self.debug: print("Nonce expired",file=sys.stderr)
                  self.remove(nonce)
                  return False
              elif ip != flask.request.remote_addr:
                  if self.debug: print("Nonce IP mismatch",file=sys.stderr)
                  self.remove(nonce)
                  return False
              else:
                  return True
          except KeyError:
              if self.debug: print("Nonce " + nonce + " does not exist",file=sys.stderr)
              return False