python2Packages.cryptography: pin to 2.9.2

pkgs/development/python-modules/cryptography/2.9.nix

···
+{ stdenv
+, buildPythonPackage
+, fetchPypi
+, fetchpatch
+, isPy27
+, ipaddress
+, openssl
+, cryptography_vectors
+, darwin
+, packaging
+, six
+, pythonOlder
+, isPyPy
+, cffi
+, pytest
+, pretend
+, iso8601
+, pytz
+, hypothesis
+, enum34
+}:
+
+buildPythonPackage rec {
+  pname = "cryptography";
+  version = "2.9.2"; # Also update the hash in vectors.nix
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "0af25w5mkd6vwns3r6ai1w5ip9xp0ms9s261zzssbpadzdr05hx0";
+  };
+
+  outputs = [ "out" "dev" ];
+
+  buildInputs = [ openssl ]
+             ++ stdenv.lib.optional stdenv.isDarwin darwin.apple_sdk.frameworks.Security;
+  propagatedBuildInputs = [
+    packaging
+    six
+  ] ++ stdenv.lib.optional (!isPyPy) cffi
+  ++ stdenv.lib.optionals isPy27 [ ipaddress enum34 ];
+
+  checkInputs = [
+    cryptography_vectors
+    hypothesis
+    iso8601
+    pretend
+    pytest
+    pytz
+  ];
+
+  checkPhase = ''
+    py.test --disable-pytest-warnings tests
+  '';
+
+  # IOKit's dependencies are inconsistent between OSX versions, so this is the best we
+  # can do until nix 1.11's release
+  __impureHostDeps = [ "/usr/lib" ];
+
+  meta = with stdenv.lib; {
+    description = "A package which provides cryptographic recipes and primitives";
+    longDescription = ''
+      Cryptography includes both high level recipes and low level interfaces to
+      common cryptographic algorithms such as symmetric ciphers, message
+      digests, and key derivation functions.
+      Our goal is for it to be your "cryptographic standard library". It
+      supports Python 2.7, Python 3.5+, and PyPy 5.4+.
+    '';
+    homepage = "https://github.com/pyca/cryptography";
+    changelog = "https://cryptography.io/en/latest/changelog/#v"
+      + replaceStrings [ "." ] [ "-" ] version;
+    license = with licenses; [ asl20 bsd3 psfl ];
+    maintainers = with maintainers; [ primeos ];
+  };
+}

pkgs/top-level/python-packages.nix

···
 
   cryptacular = callPackage ../development/python-modules/cryptacular { };
 
-  cryptography = callPackage ../development/python-modules/cryptography { };
+  cryptography = if isPy27 then
+      callPackage ../development/python-modules/cryptography/2.9.nix { }
+    else
+      callPackage ../development/python-modules/cryptography { };
 
   cryptography_vectors = callPackage ../development/python-modules/cryptography/vectors.nix { };