Find any missing environment variables

def find_missing_env(self):
        """Find any missing environment variables"""
        missing = []
        for e in self.env:
            if e.default_val is None and e.set_val is None:
                if e.env_name not in os.environ:
                    missing.append(e.env_name)

        if missing:
            raise BadOption("Some environment variables aren't in the current environment", missing=missing)