# print messages to STDERR
# shellcheck shell=bash
function error() {
  echo >&2 "[$(date +'%Y-%m-%dT%H:%M:%S')] ERROR: $1"
  shift
  for msg in "$@"; do echo >&2 "$msg"; done
  exit 1
}
function log() {
  echo >&2 "[$(date +'%Y-%m-%dT%H:%M:%S')] $1"
  shift
  for msg in "$@"; do echo >&2 "$msg"; done
}