Task was destroyed but it is pending!

[strarsis]

After sending mysqld a SIGTERM singal to shut it down,
chaperone detects this but an error message occurs.

mysqld.conf for mariadb/mysql official Dockerhub image:

# mysqld.conf

settings: {
  env_set: {
    "MYSQL_PID_FILE":  "/run/mysqld/mysqld.pid"
  },
  env_inherit: [
    "MYSQL_ROOT_PASSWORD",
    "MYSQL_DATABASE",
    "MYSQL_USER",
    "MYSQL_PASSWORD",
    "MYSQL_ALLOW_EMPTY_PASSWORD",
    "MYSQL_RANDOM_ROOT_PASSWORD",
    "MYSQL_ONETIME_PASSWORD"
  ]
}

mysql1.service: {
  type: forking,
  command: "mysqld",
  enabled: false,
  uid: mysql,
  gid: mysql,
  service_groups: database,
  pidfile: "$(MYSQL_PID_FILE)",
}

# setup script starts also mysqld
mysql.service: {
  type: simple,
  command: "/docker-entrypoint.sh mysqld",
    # Dockerfile entrypoint + default cmd
  uid: root,
  gid: root,
  pidfile: "$(MYSQL_PID_FILE)",
  process_timeout: 60,
  restart: true,
  enabled: true,
  stderr: "log",
  service_groups: database,
}

$ docker exec test killall -s SIGTERM mysqld

Docker log:

Dec  6 12:33:13 e1588f1e7257 mysql[152]: 2016-12-06 12:33:13 140467036891072 [Note] mysqld (mysqld 10.1.19-MariaDB-1~jessie) starting as process 9 ...
Dec  6 12:35:00 e1588f1e7257 chaperone[1]: REAP pid=9,status=0
Dec  6 12:35:00 e1588f1e7257 chaperone[1]: no child processes present
Dec  6 12:35:00 e1588f1e7257 chaperone[1]: mysql.service exit status for pid=9 is '<ProcStatus exit_status=0>'
Dec  6 12:35:00 e1588f1e7257 chaperone[1]: Final termination phase.
Task was destroyed but it is pending!
task: <Task pending coro=<_monitor_service() running at /usr/local/lib/python3.4/dist-packages/chaperone/cproc/pt/simple.py:29> wait_for=<Future pending cb=[Task._wakeup()]> cb=[SubProcess.add_pending.<locals>.<lambda>() at /usr/local/lib/python3.4/dist-packages/chaperone/cproc/subproc.py:631]>

The mysql process should have been restarted by chaperone,
but it terminated completely and the Docker container stopped.