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 __exit__(self, exc_type, exc_value, traceback):
        connection = get_connection(self.using)
        try:
            self._no_monkey.__exit__(self, exc_type, exc_value, traceback)
        except DatabaseError:
            transaction_states[self.using].rollback()
        else:
            if not connection.closed_in_transaction and exc_type is None and \
                    not connection.needs_rollback:
                if transaction_states[self.using]:
                    transaction_states[self.using].commit()
            else:
                transaction_states[self.using].rollback()