A recent update to cffi that was yanked is still being installed on our
Mac OS X 10.11 test image since the version of pip there is very old and
does not ignore yanked packages.
Pin the version of pyOpenSSL and its dependencies to fix this and avoid
future spontaneous failures.
Change:
New `cryptography` statically links an openssl that is too new for macOS
10.11, so limit to an older cryptography for now.
Test Plan:
Ran the test with `--remote osx/10.11` and it passed.
Signed-off-by: Rick Elrod <rick@elrod.me>
