[IMPR] use str.format method usability
[IMPR] use str.format method usability

use str.format instead of concating indexed variables

Change-Id: Ic1c053da3e6c0a53c663ba4d4e8bf6284789f469

wikimedia/pywikibot-core,PersianWikipedia/pywikibot-core,wikimedia/pywikibot-core