在安装airflow后，初始化遇到这样的问题

Traceback (most recent call last):
  File "/opt/anaconda3/bin/airflow", line 32, in <module>
    args.func(args)
  File "/opt/anaconda3/lib/python3.7/site-packages/airflow/bin/cli.py", line 1102, in initdb
    db.initdb(settings.RBAC)
  File "/opt/anaconda3/lib/python3.7/site-packages/airflow/utils/db.py", line 106, in initdb
    upgradedb()
  File "/opt/anaconda3/lib/python3.7/site-packages/airflow/utils/db.py", line 377, in upgradedb
    command.upgrade(config, 'heads')
  File "/opt/anaconda3/lib/python3.7/site-packages/alembic/command.py", line 298, in upgrade
    script.run_env()
  File "/opt/anaconda3/lib/python3.7/site-packages/alembic/script/base.py", line 489, in run_env
    util.load_python_file(self.dir, "env.py")
  File "/opt/anaconda3/lib/python3.7/site-packages/alembic/util/pyfiles.py", line 98, in load_python_file
    module = load_module_py(module_id, path)
  File "/opt/anaconda3/lib/python3.7/site-packages/alembic/util/compat.py", line 173, in load_module_py
    spec.loader.exec_module(module)
  File "<frozen importlib._bootstrap_external>", line 728, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/opt/anaconda3/lib/python3.7/site-packages/airflow/migrations/env.py", line 92, in <module>
    run_migrations_online()
  File "/opt/anaconda3/lib/python3.7/site-packages/airflow/migrations/env.py", line 86, in run_migrations_online
    context.run_migrations()
  File "<string>", line 8, in run_migrations
  File "/opt/anaconda3/lib/python3.7/site-packages/alembic/runtime/environment.py", line 846, in run_migrations
    self.get_context().run_migrations(**kw)
  File "/opt/anaconda3/lib/python3.7/site-packages/alembic/runtime/migration.py", line 518, in run_migrations
    step.migration_fn(**kw)
  File "/opt/anaconda3/lib/python3.7/site-packages/airflow/migrations/versions/0e2a74e0fc9f_add_time_zone_awareness.py", line 45, in upgrade
    "Global variable explicit_defaults_for_timestamp needs to be on (1) for mysql"
Exception: Global variable explicit_defaults_for_timestamp needs to be on (1) for mysql

解决方法：
进入mysql airflow 数据库，设置global explicit_defaults_for_timestamp

mysql>  show global variables like '%timestamp%';
+---------------------------------+-------+
| Variable_name                   | Value |
+---------------------------------+-------+
| explicit_defaults_for_timestamp | OFF   |
| log_timestamps                  | UTC   |
+---------------------------------+-------+
2 rows in set (0.00 sec)

mysql> set global explicit_defaults_for_timestamp =1;
Query OK, 0 rows affected (0.00 sec)

mysql>