Find approvals issued for a specific client.

def ApprovalFind(object_id, token=None):
  """Find approvals issued for a specific client."""
  user = getpass.getuser()
  object_id = rdfvalue.RDFURN(object_id)
  try:
    approved_token = security.Approval.GetApprovalForObject(
        object_id, token=token, username=user)
    print("Found token %s" % str(approved_token))
    return approved_token
  except access_control.UnauthorizedAccess:
    print("No token available for access to %s" % object_id)