(bug 66619) API change: error message is a list not a dict
(bug 66619) API change: error message is a list not a dict

Solve breaking change of gerrit 124323 and keep the old code
part for backward compatibility with older mw releases.

Change-Id: I7dc2c03ce0d84ea2d5c36170998253b4b8fed3ae

hasteur/g13bot_tools_new,emijrp/pywikibot-core,darthbhyrava/pywikibot-local,TridevGuha/pywikibot-core,magul/pywikibot-core,smalyshev/pywikibot-core,valhallasw/pywikibot-core,h4ck3rm1k3/pywikibot-core,VcamX/pywikibot-core,happy5214/pywikibot-core,Darkdadaah/pywikibot-core,magul/pywikibot-core,jayvdb/pywikibot-core,hasteur/g13bot_tools_new,npdoty/pywikibot,wikimedia/pywikibot-core,PersianWikipedia/pywikibot-core,happy5214/pywikibot-core,jayvdb/pywikibot-core,h4ck3rm1k3/pywikibot-core,npdoty/pywikibot,wikimedia/pywikibot-core,icyflame/batman,hasteur/g13bot_tools_new,Darkdadaah/pywikibot-core,xZise/pywikibot-core,trishnaguha/pywikibot-core