Support pyparsing v3 (AttributeError downcaseTokens) #207
Description
There appears to be a use of a discontinued feature from the pyparsing library:
Traceback (most recent call last):
[...]
File "/usr/local/lib/python3.9/dist-packages/httplib2/__init__.py", line 52, in <module>
from . import auth
File "/usr/local/lib/python3.9/dist-packages/httplib2/auth.py", line 20, in <module>
auth_param_name = token.copy().setName("auth-param-name").addParseAction(pp.downcaseTokens)
AttributeError: module 'pyparsing' has no attribute 'downcaseTokens'