python - pandas pythonでのSQLクエリ

Question

私はpython pandasでSQLクエリを書いています:

import pandas as pd
from pandas import DataFrame, read_csv
import numpy as np
from pandasql import sqldf
pysqldf=lambda q:sqldf(q,globals())
rolup = pysqldf(u"select MasterUserId,DeviceUsed,hcluster, count(MasterUserId) as Tot_Rec, sum(Visits),sum(PV),sum(TimeSpent) from clstrd_data group by MasterUserId,DeviceUsed,hcluster;")

エラー：

sqlite3.ProgrammingError: You must not use 8-bit bytestrings unless you use a text_factory that can interpret 8-bit bytestrings (like text_factory = str). It is highly recommended that you instead just switch your application to Unicode strings.

Unicode 文字列に切り替えるには? 私はpython2.7を使用しています。