* Misc CI cleanups

- Update branch names to match upstream
- Drop py2 testing

* Appease stricter checking in latest Sphinx to get CI passing again

* Don't accidentally delete an important line from tox.ini

* Give py2 support a brief stay of execution

As requested by @reaperhulk on IRC

* add Context.set_*_proto_version, fix #860

* docs: add new openssl tls methods

* accept the fact that nothing can be taken for granted

* bump minimum required cryptography version to 3.3

* drop support for Python 3.5

* use binary wheels for cryptography

* Revert "use binary wheels for cryptography"

This reverts commit 91a04c612ed1d0dd9fd541dfefe21cac7c25b1c1.

* docker ci: compile cryptography with rust

Deprecated under OpenSSL 1.1

Signed-off-by: Rosen Penev <rosenp@gmail.com>

* Tox.ini; Test on Python 3.9 and make flake8 stricter

* max-line-length = 88

* Remove unused import

* Update tox.ini

* Use PEP8 line length

* Use PEP8 line length

* ALPN: complete handshake without accepting a client's protocols.

The callback passed to `SSL_CTX_set_alpn_select_cb` can return
`SSL_TLSEXT_ERR_NOACK` to allow the handshake to continue without
accepting any of the client's offered protocols.

This commit introduces `NO_OVERLAPPING_PROTOCOLS`, which the Python
callback passed to `Context.set_alpn_select_callback` can return to
achieve the same thing.

It does not change the previous meaning of an empty string, which
still terminates the handshake.

* Update src/OpenSSL/SSL.py

Co-Authored-By: Alex Gaynor <alex.gaynor@gmail.com>

* Address @alex's review.

* Use recorded value in test, fix lint error.

* Cover TypeError branch in _ALPNHelper.callback

* Expose OP_NO_TLSv1_3

* Support openssl <1.1.1