mysql1193 HY000,MySQL ERROR 1193 (HY000): Unknown system variable 'validate_password_policy'

mysql> set  global  validate_password.policy =0;
ERROR 1193 (HY000): Unknown system variable 'policy'
mysql> ERROR 1193 (HY000): Unknown system variable 'policy'
    ->
    -> ;
ERROR 1064 (42000): You have an error 
 
in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'ERROR 1193 (HY000): Unknown system variable 'policy'' at line 1
mysql> SHOW VARIABLES LIKE 'validate_password%';
+--------------------------------------+--------+
| Variable_name                        | 
 
Value  |
+--------------------------------------+--------+
| validate_password_check_user_name    | OFF    |
| validate_password_dictionary_file    |        |
| validate_password_length             | 8      |
| validate_password_mixed_case_count   | 1      |
| validate_password_number_count       | 1      |
| validate_password_policy             | MEDIUM |
| validate_password_special_char_count | 1      |
+--------------------------------------+--------+
 

7 rows in set (0.01 sec)

mysql> select plugin_name, plugin_status from information_schema.plugins where plugin_name like 'validate%';
+-------------------+---------------+
| plugin_name       | plugin_status |
+-------------------+---------------+
| validate_password | ACTIVE        |
+-------------------+---------------+
1 row in set (0.00 sec)

mysql> install plugin validate_password soname 'validate_password.so';
ERROR 1125 (HY000): Function 'validate_password' already exists
mysql> select plugin_name, plugin_status from information_schema.plugins where plugin_name like 'validate%';
+-------------------+---------------+
| plugin_name       | plugin_status |
+-------------------+---------------+
| validate_password | ACTIVE        |
+-------------------+---------------+
1 row in set (0.00 sec)

mysql>  SHOW VARIABLES LIKE 'validate_password%';
+--------------------------------------+--------+
| Variable_name                        | Value  |
+--------------------------------------+--------+
| validate_password_check_user_name    | OFF    |
| validate_password_dictionary_file    |        |
| validate_password_length             | 8      |
| validate_password_mixed_case_count   | 1      |
| validate_password_number_count       | 1      |
| validate_password_policy             | MEDIUM |
| validate_password_special_char_count | 1      |
+--------------------------------------+--------+
7 rows in set (0.00 sec)

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

mysql> set global validate_password.length=1;
ERROR 1193 (HY000): Unknown system variable 'length'
mysql>