def METHOD_NAME(contents):
    errors_lines = []
    for i, line in enumerate(contents.splitlines()):
        # Don't print newlines
        line = line.rstrip('\n')
        invalid_code_unit_indices = []
        indicator_code_units = []
        for code_unit in line:
            if ord(code_unit) > 256:
                invalid_code_unit_indices.append(i)
                indicator_code_units.append('^')
            else:
                indicator_code_units.append(' ')
        if invalid_code_unit_indices:
            errors_lines.append(f'    | {line}')
            errors_lines.append(f'    | {"".join(indicator_code_units)}')
    if errors_lines:
        errors_lines.insert(0, '    readme contains non-ASCII character(s)')
    return errors_lines