Why this is a problem?
When something goes wrong at module intallation time (for example, internet connection broke) and table was created but module doesn't installed correctly than it's imposible to reinstall module. I removed module and enable again and got this error message:

DatabaseSchemaObjectExistsException: Таблица pgapi_transaction уже существует. в функции DatabaseSchema->createTable() (строка 652 в файле /home/user/example.com/includes/database/schema.inc).