I can't login with root ,I think root's password may be changed.But I can't change root's password either.

Mysql version is v8.0.16. 

I have used `--init-file` to specificd alter sql at mysqld booting

```
alter user 'root'@'localhost' identified by 'mynewpassword'

```

but it doesn't work.

I used `--skip-grant-tables --user=mysql` so I could add a new user, and my new user works. I try to alter root,but it failed again.

```sql
mysql> alter user 'root'@'localhost' identified by 'mynewpassword';
ERROR 1396 (HY000): Operation ALTER USER failed for 'root'@'localhost'

```

here is the table user's content

```sql
mysql> select user,host from user;
+------------------+-----------+
| user             | host      |
+------------------+-----------+
| admin            | %         |
| mysql.infoschema | localhost |
| mysql.session    | localhost |
| mysql.sys        | localhost |
| root             | localhost |
+------------------+-----------+

```

Do anyone have any idea?