ARO-3536: Add error handling when "CLUSTER" env variable is empty. (#…

…3007)

* ARO-3536: Add error handling when "CLUSTER" env variable is empty.
* ARO-3536: Include empty string validation
* ARO-3536: Refactor variable names and include variable name in error message.

pkg/env/env.go

@@ -123,9 +123,9 @@ func IsCI() bool {
 // if it does not exist an environment variable with that name, it will return an error.
 // Otherwise it returns nil.
 func ValidateVars(vars ...string) error {
-	for _, v := range vars {
-		if _, found := os.LookupEnv(v); !found {
-			return fmt.Errorf("environment variable %q unset", v)
+	for _, envName := range vars {
+		if envValue, found := os.LookupEnv(envName); !found || envValue == "" {
+			return fmt.Errorf("environment variable %q unset", envName)
 		}
 	}
 	return nil