Improve error messages a little bit.
Improve error messages a little bit.

Cremator/vanitygen,enlighter/vanitygen,bither/vanitygen,bespike/vanitygen,isghe/vanitygen,sobakasu/vanitygen,kangaderoo/vanitygen,inuitwallet/vanitygen,kangaderoo/vanitygen,WyseNynja/vanitygen,WyseNynja/vanitygen,dooglus/vanitygen,fantomgs/vanitygen,sobakasu/vanitygen,sobakasu/vanitygen,samr7/vanitygen,clovermebitcoin/test,Instigo/vanitygen,Gamecredits-Universe/vanitygen-gamecredits,enlighter/vanitygen,kangaderoo/vanitygen,shinohai/vanitygen,dooglus/vanitygen,Stoner19/NEOS-vanitygen,clovermebitcoin/test,colindean/vanitygen,Cremator/vanitygen