Verify ISO exists before releasing binaries

Makefile

@@ -397,6 +397,10 @@ reportcard: ## Run goreportcard for minikube
 mdlint:
 	@$(MARKDOWNLINT) $(MINIKUBE_MARKDOWN_FILES)
 
+.PHONY: verify-iso
+verify-iso: # Make sure the current ISO exists in the expected bucket
+	gsutil stat gs://$(ISO_BUCKET)/minikube-$(ISO_VERSION).iso
+
 out/docs/minikube.md: $(shell find "cmd") $(shell find "pkg/minikube/constants") pkg/minikube/assets/assets.go pkg/minikube/translate/translations.go
 	go run -ldflags="$(MINIKUBE_LDFLAGS)" -tags gendocs hack/help_text/gen_help_text.go
 

hack/jenkins/release_build_and_upload.sh

@@ -38,6 +38,10 @@ grep -E "^VERSION_BUILD \\?=" Makefile | grep "${VERSION_BUILD}"
 # Force go packages to the Jekins home directory
 export GOPATH=$HOME/go
 
+# Verify ISO exists
+echo "Verifying ISO exists ..."
+make verify-iso
+
 # Build and upload
 env BUILD_IN_DOCKER=y \
   make -j 16 \