Playing with this a bit more confirms MySQL query isn't crafted correctly by alembic:
```
mysql> ALTER TABLE quark_ip_addresses ADD UNIQUE (subnet_id, address);
ERROR 1280 (42000): Incorrect index name 'subnet_id'
mysql> ALTER TABLE quark_ip_addresses ADD UNIQUE (`subnet_id`, `address`);                                                                                                           
ERROR 1280 (42000): Incorrect index name 'subnet_id'
mysql> ALTER TABLE quark_ip_addresses ADD UNIQUE subnet_id (`subnet_id`, `address`);                                                                                                 
ERROR 1280 (42000): Incorrect index name 'subnet_id'
mysql> ALTER TABLE quark_ip_addresses ADD UNIQUE subnet_id_address (`subnet_id`, `address`);                                                                                         
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0
```