fix: negative sleeps IOError 22
fix: negative sleeps IOError 22

holiman/pyethereum,pipermerriam/pyethereum,pipermerriam/pyethereum,shahankhatch/pyethereum,shahankhatch/pyethereum,ethereum/pyethereum,ddworken/pyethereum,ckeenan/pyethereum,ethereum/pyethereum,harlantwood/pyethereum,jnnk/pyethereum,ethermarket/pyethereum,inzem77/pyethereum,karlfloersch/pyethereum,vaporry/pyethereum,karlfloersch/pyethereum