ElastAlert 安装报错，有没人遇到啊 ModuleNotFoundError: No module named 'apscheduler'

执行  python -m elastalert.elastalert --verbose --rule example_rules/example_test.yaml
然后报错
Traceback (most recent call last):
  File "/root/ENTER/lib/python3.7/runpy.py", line 183, in _run_module_as_main
    mod_name, mod_spec, code = _get_module_details(mod_name, _Error)
  File "/root/ENTER/lib/python3.7/runpy.py", line 109, in _get_module_details
    __import__(pkg_name)
  File "/opt/elastalert/elastalert/elastalert.py", line 22, in <module>
    from apscheduler.schedulers.background import BackgroundScheduler
ModuleNotFoundError: No module named 'apscheduler'