Compile env, client_env, shell and client_shell commands

def expand_defaults(self, client=False, getenv=True, getshell=True):
        """Compile env, client_env, shell and client_shell commands
        """
        if not isinstance(self._default, six.string_types):
            self.expanded_default = self._default
        else:
            self.expanded_default = coerce(self.type, expand_defaults(
                self._default, client, getenv, getshell))