block2.python

def send_slack_alert(context=None):
    """Send slack alert on failure to alert the team"""
    payload_vars = {
        'url': 'https://hooks.slack.com/services/<YOUR_CREDENTIALS_HERE>',
        'run_id': str(context['run_id']),
        'task': str(context['task']),
        'dag_name': str(context['dag'].dag_id)
    }
    error_message = "{dag_name} Failure! Task failed: {task} Check log at: {run_id}".format(**payload_vars)
    payload_vars['json'] = """payload={{"channel":"#<YOUR_CHANNEL_HERE>","text":"{0}"}}""".format(error_message)
    slack_cmd = """curl
    -X POST \
    --data-urlencode '{json}' \
    {url}""".format(**payload_vars)
    slack_alert = BashOperator(
        task_id='slack_alert',
        dag=dag,
        bash_command=slack_cmd
    )
    slack_alert.execute(context)