def METHOD_NAME():
    conn = boto3.client("managedblockchain", region_name="us-east-1")
    with pytest.raises(ClientError) as ex:
        conn.create_proposal(
            NetworkId="n-ABCDEFGHIJKLMNOP0123456789",
            MemberId="m-ABCDEFGHIJKLMNOP0123456789",
            Actions=helpers.default_policy_actions,
        )
    err = ex.value.response["Error"]
    assert err["Code"] == "ResourceNotFoundException"
    assert "Network n-ABCDEFGHIJKLMNOP0123456789 not found" in err["Message"]