layers of bugs

1. While _fetchSingle method could raise exceptions, but we don't try to catch these exceptions when we calling _fetchSingle (_singleValue method calls it).
2. because the prototype of the Task.taskRequest method likes follows, hence strict parameter cannot pass to _singleValue method even we pass it all return values of locals()

    def getRequest(self):
            id = self.id                                                                                                                                                                                        
            query = """SELECT request FROM task WHERE id = %(id)i"""                                                                                                                                            
            xml_request = _singleValue(query, locals())
            ... ...
   

PR here: https://pagure.io/koji/pull-request/217