def pre_export(output, conanfile, conanfile_path, reference, **kwargs):
    # Check basic meta-data
    for field in ["url", "license", "description"]:
        field_value = getattr(conanfile, field, None)
        if not field_value:
            output.warn("Conanfile doesn't have '%s'. It is recommended to add it as attribute"
                        % field)