def fix_old_requirements_txt(reqs_in):
    """Add common missing requirements"""
    result = [reqs_in]
    reqs_set = set(reqs_in.splitlines())
    if 'naucse_render<1.0' in reqs_set:
        result.append('')
        result.append('# compatibility requirements')
        result.append('naucse_render < 1.4')
        result.append('nbconvert < 6')

    return '\n'.join(result)