removed unused method and minor pylint fix

torba/basedatabase.py

@@ -150,14 +150,6 @@ class SQLiteMixin:
         )
         return sql, values
 
-    @defer.inlineCallbacks
-    def query_one_value(self, query, params=None, default=None):
-        result = yield self.run_query(query, params)
-        if result:
-            return result[0][0] or default
-        else:
-            return default
-
     @staticmethod
     def execute(t, sql, values):
         log.debug(sql)