def __init__(self, package, version):
        """Construct a new requirement.

        :param package: the package name.
        :param version: a semver compatible version specification.
        """
        self.package = package
        self.version = version
        if self.version and not re.match(r"[<=>~]", version[:2]):
            self.version = "=={}".format(self.version)
def test_config_errors(self):
        Session = scoped_session(sa.orm.sessionmaker())

        s = Session()  # noqa
        assert_raises_message(
            sa.exc.InvalidRequestError,
            "Scoped session is already present",
            Session,
            bind=testing.db,
        )

        assert_warns_message(
            sa.exc.SAWarning,
            "At least one scoped session is already present. ",
            Session.configure,
            bind=testing.db,
        )