'error.user_exists' => 'このログインと関連されたユーザーは既に存在します。',
// TODO: translate the following.
// 'error.object_exists' => 'Object with this name already exists.',
-// 'error.task_exists' => 'Task with this name already exists.',
// 'error.client_exists' => 'Client with this name already exists.',
// 'error.invoice_exists' => 'Invoice with this number already exists.',
// TODO: translate the following.