终端里面运行tornado自带的demos里面的blog.py，反馈出错，是编码方式出错了吗？
File "/Library/Python/2.7/site-packages/tornado-2.4-py2.7.egg/tornado/database.py", line 59, in __init__
args = dict(conv=CONVERSIONS, use_unicode=True, charset="utf8",
NameError: global name 'CONVERSIONS' is not defined
