<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def _usernamesToSidObjects(cls, val, **kwargs):
        '''
        converts a list of usernames to sid objects
        '''
        if not val:
            return val
        if isinstance(val, six.string_types):
            val = val.split(',')
        sids = []
        for _user in val:
            try:
                sid = win32security.LookupAccountName('', _user)[0]
                sids.append(sid)
            # This needs to be more specific
            except Exception as e:
                log.exception('Handle this explicitly')
                raise CommandExecutionError((
                    'There was an error obtaining the SID of user "{0}". Error '
                    'returned: {1}'
                    ).format(_user, e))
        return sids