'Removes an alias.
Raises ValueError if there is not at least one other nick in the group.
To delete an entire group, use `delete_group`.'

def unalias_nick(self, alias):

    alias = Identifier(alias)
    nick_id = self.get_nick_id(alias, False)
    count = self.execute(u'SELECT    COUNT(*)    FROM    nicknames    WHERE    nick_id    =    ?', [nick_id]).fetchone()[0]
    if (count <= 1):
        raise ValueError(u'Given    alias    is    the    only    entry    in    its    group.')
    self.execute(u'DELETE    FROM    nicknames    WHERE    slug    =    ?', [alias.lower()])
