Fix KeyError on incorrect genesis hash (#224)
Fix KeyError on incorrect genesis hash (#224)

Fix KeyError that occurs when creating an exception for an incorrect genesis hash.
thelazier/electrumx,Groestlcoin/electrumx-grs,Crowndev/electrumx,shsmith/electrumx,Crowndev/electrumx,shsmith/electrumx,erasmospunk/electrumx,erasmospunk/electrumx,thelazier/electrumx,Groestlcoin/electrumx-grs