docker-env: improve template error handling
docker-env: improve template error handling

warmchang/minikube,endocode/minikube,dlorenc/minikube,kubernetes/minikube,dongsupark/minikube,dlorenc/minikube,warmchang/minikube,kubernetes/minikube,kubernetes/minikube,dims/minikube,dalehamel/minikube,mikegrass/minikube,abbytiz/minikube,kubernetes/minikube,mikegrass/minikube,dims/minikube,skipjaq/minikube,aaron-prindle/minikube,cu12/minikube,warmchang/minikube,warmchang/minikube,skipjaq/minikube,skipjaq/minikube,dalehamel/minikube,kubernetes/minikube,dlorenc/minikube,cu12/minikube,dlorenc/minikube,warmchang/minikube,dlorenc/minikube,abbytiz/minikube,kubernetes/minikube,dongsupark/minikube,r2d4/minikube,aaron-prindle/minikube,abbytiz/minikube,dongsupark/minikube,mikegrass/minikube,cu12/minikube,warmchang/minikube,r2d4/minikube,dlorenc/minikube,dims/minikube,endocode/minikube,aaron-prindle/minikube,dlorenc/minikube,dalehamel/minikube,endocode/minikube,dlorenc/minikube,r2d4/minikube,kubernetes/minikube,warmchang/minikube