具体解决如下：
Inside site-packages/requests/packages/urllib3/fields.py, delete this (line ~50):
value = email.utils.encode_rfc2231(value, ‘utf-8’)
And change the line right underneath it to this:
value = ‘%s=”%s”‘ % (name, value)
This makes servers (that I’ve tested) pick up the field and process it correctly.
https://github.com/kennethreitz/requests/issues/2117 ~issues!
这个东西折磨了3个多小时，一直以为是自己代码写错了，疯狂debug，心力交瘁啊…
记住了,下次用requests库写有中文的要改库文件…