exc.py 文件源码

def instance(cls, statement, params,
                        orig,
                        dbapi_base_err,
                        connection_invalidated=False):
        # Don't ever wrap these, just return them directly as if
        # DBAPIError didn't exist.
        if isinstance(orig, (KeyboardInterrupt, SystemExit, DontWrapMixin)):
            return orig

        if orig is not None:
            # not a DBAPI error, statement is present.
            # raise a StatementError
            if not isinstance(orig, dbapi_base_err) and statement:
                msg = traceback.format_exception_only(
                    orig.__class__, orig)[-1].strip()
                return StatementError(
                    "%s (original cause: %s)" % (str(orig), msg),
                    statement, params, orig
                )

            name, glob = orig.__class__.__name__, globals()
            if name in glob and issubclass(glob[name], DBAPIError):
                cls = glob[name]

        return cls(statement, params, orig, connection_invalidated)