Map Bcache's size strings to real bytes

def _size_map(size):
    '''
    Map Bcache's size strings to real bytes
    '''
    try:
        # I know, I know, EAFP.
        # But everything else is reason for None
        if not isinstance(size, int):
            if re.search(r'[Kk]', size):
                size = 1024 * float(re.sub(r'[Kk]', '', size))
            elif re.search(r'[Mm]', size):
                size = 1024**2 * float(re.sub(r'[Mm]', '', size))
            size = int(size)
        return size
    except Exception:
        return None