* HTTP Handler class annotations for py2/urllib2 & py3/urllib.request
Add full annotations for the following classes:
* Python 2:
* `urllib2.AbstractHTTPHandler`
* `urllib2.HTTPHandler`
* `urllib2.HTTPsHandler`
* Python 3:
* `urllib.request.AbstractHTTPHandler`
* `urllib.request.HTTPHandler`
* `urllib.request.HTTPsHandler`
This information is largely undocumented, and was obtained by directly examining
the Python source code:
* Python 2 (v2.7.15) - https://github.com/python/cpython/blob/v2.7.15/Lib/urllib2.py#L1115-L1243
* Python 3 (v3.7.1) - https://github.com/python/cpython/blob/v3.7.1/Lib/urllib/request.py#L1224-L1364
`urllib2.AbstractHTTPHandler.do_open` takes as a parameter either
`HTTPConnection` or `HTTPSConnection`--one of the classes, not an instance of
either--and constructs an object using only a few of the parameters that either
constructor could use. `HTTPConnectionProtocol` in `stdlib/2/httplib.pyi`
follows a similar patten to `HTTPConnectionProtocol` added to
`stdlib/3/http/client.pyi` in pull request #2582 to describe the type of the
`http_class` that is passed to `do_open`.
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