not support HTTP2 header

[geebadan]

not support http2 header

example:

import requests
from hyper.contrib import HTTP20Adapter

headers={':path': '/hello}'

s = requests.Session()
s.mount('https://http2bin.org', HTTP20Adapter())
r = s.get('https://http2bin.org/get', headers=headers)
print(r.status_code)

# raise Invalid leading whitespace, reserved character(s), or return character(s) in header name: ':path'

[sigmavirus24]

This is a duplicate