add `Connection.set_verify`, fix #255 (#1073)

* add `Connection.set_verify`, fix #255

* show that it works with cryptography main

* Revert "show that it works with cryptography main"

This reverts commit fb0136a8e5aa5d2c6e0c16f8f4ecee2f3c72a16b.

* make it black
3 files changed