Without this, `db:structure:dump` task raises an error as follwing:

```
can't modify frozen String
activerecord/lib/active_record/tasks/sqlite_database_tasks.rb:77:in `run_cmd_error'
activerecord/lib/active_record/tasks/sqlite_database_tasks.rb:72:in `run_cmd'
activerecord/lib/active_record/tasks/sqlite_database_tasks.rb:52:in `structure_dump'
activerecord/lib/active_record/tasks/database_tasks.rb:219:in `structure_dump'
activerecord/lib/active_record/railties/databases.rake:279:in `block (3 levels) in <main>'
railties/lib/rails/commands/rake/rake_command.rb:23:in `block in perform'
railties/lib/rails/commands/rake/rake_command.rb:20:in `perform'
railties/lib/rails/command.rb:48:in `invoke'
railties/lib/rails/commands.rb:18:in `<main>'
```