关于 PHP artisan migrate 报错问题?

In Connection.php line 664:

SQLSTATE[42000]: Syntax error or access violation: 1071 Specified key was too long; max
key length is 767 bytes (SQL: alter table users add unique users_email_unique(email ))

In Connection.php line 458:

SQLSTATE[42000]: Syntax error or access violation: 1071 Specified key was too long; max
key length is 767 bytes

这是报错内容 mysql版本5.6.38