[IMPROV] tests: More information on intersect fail
[IMPROV] tests: More information on intersect fail

Instead of just comparing the lengths it should also tell which items
are missing/duplicates.

Change-Id: I2d8b60749f0c25b036139237effbc84d05d4d766

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