Parse the aliases file, and return a list of line components:

    [
      (alias1, target1, comment1),
      (alias2, target2, comment2),
    ]

def __parse_aliases():
    '''
    Parse the aliases file, and return a list of line components:

    [
      (alias1, target1, comment1),
      (alias2, target2, comment2),
    ]
    '''
    afn = __get_aliases_filename()
    ret = []
    if not os.path.isfile(afn):
        return ret
    with salt.utils.files.fopen(afn, 'r') as ifile:
        for line in ifile:
            line = salt.utils.stringutils.to_unicode(line)
            match = __ALIAS_RE.match(line)
            if match:
                ret.append(match.groups())
            else:
                ret.append((None, None, line.strip()))
    return ret