fix: raise catchable exception on wrong signature
fix: raise catchable exception on wrong signature

ethereum/pyethereum,karlfloersch/pyethereum,shahankhatch/pyethereum,ethereum/pyethereum,vaporry/pyethereum,holiman/pyethereum,ckeenan/pyethereum,karlfloersch/pyethereum,pipermerriam/pyethereum,pipermerriam/pyethereum,inzem77/pyethereum,shahankhatch/pyethereum