improve error handling
improve error handling

vmware/rbvmomi,rcorrieri/rbvmomi,10xEngineer/rbvmomi,10xEngineer/rbvmomi,rapid7/rbvmomi,frapposelli/vagrant-rbvmomi,logankimmel/rbvmomi,rapid7/rbvmomi,omar-infinio/rbvmomi,frapposelli/vagrant-rbvmomi