Fix and improve migration code
Fix and improve migration code

It was a wrong initialization of NoOptionError class. It's better to
check for NoSectionError exception.

f2nd/yandex-tank,nettorta/yandex-tank,yandex/yandex-tank,netortik/yandex-tank,fomars/yandex-tank,nettorta/yandex-tank,fomars/yandex-tank,f2nd/yandex-tank,netortik/yandex-tank,yandex/yandex-tank