<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def format_hexadecimal_field(spec, prec, number, locale):
 """Formats a hexadeciaml field."""

    if number < 0:
        # Take two's complement.
        number &= (1 << (8 * int(math.log(-number, 1 << 8) + 1))) - 1
    format_ = u'0%d%s' % (int(prec or 0), spec)
    return format(number, format_)