logging handler: may raise error on some mac

[wjo1212]

Traceback (most recent call last):
File "log_test.py", line 5, in
from aliyun.log import *
File "/Library/Python/2.7/site-packages/aliyun_log_python_sdk-0.6.45-py2.7.egg/aliyun/log/init.py", line 39, in
from .logger_hanlder import SimpleLogHandler, QueuedLogHandler, LogFields, UwsgiQueuedLogHandler
File "/Library/Python/2.7/site-packages/aliyun_log_python_sdk-0.6.45-py2.7.egg/aliyun/log/logger_hanlder.py", line 57, in
BUILTIN_LOG_FIELDS_NAMES.update(set(LogFields[x].value for x in BUILTIN_LOG_FIELDS_NAMES))
File "/Library/Python/2.7/site-packages/aliyun_log_python_sdk-0.6.45-py2.7.egg/aliyun/log/logger_hanlder.py", line 57, in
BUILTIN_LOG_FIELDS_NAMES.update(set(LogFields[x].value for x in BUILTIN_LOG_FIELDS_NAMES))
TypeError: 'type' object has no attribute 'getitem'

root cause:
seems it's using builtin enum which doesn't support [x] operations.