nix stuff

  idna2_5 = pythonPackages.idna.override rec {
    version = "2.5";
    name = "idna-${version}";

    src = pkgs.fetchurl {
      url = "mirror://pypi/i/idna/${name}.tar.gz";
      sha256 = "0frxgmgi234lr9hylg62j69j4ik5zhg0wz05w5dhyacbjfnrl68n";
    };
  };

  cryptography_vectors1_9 = pythonPackages.cryptography_vectors.override rec {
    name = "cryptography_vectors-${version}";
    version = "1.9";

    src = pkgs.fetchurl {
      url = "mirror://pypi/c/cryptography-vectors/${name}.tar.gz";
      sha256 = "1wvq1p1viam1diz9x6d61x1bsy6cninv7cjgd35x9ffig9r6gxxv";
    };
  };

  cryptography1_9 = pythonPackages.cryptography.override rec {
    name = "cryptography-${version}";
    version = "1.9";

    src = pkgs.fetchurl {
      url = "mirror://pypi/c/cryptography/${name}.tar.gz";
      sha256 = "10j8r1s29f4h59kp3mla14g588rm7qpn90nrczijk03i49q3662m";
    };

    buildInputs = [
      idna2_5
      cryptography_vectors1_9

      pkgs.openssl
      pythonPackages.pretend
      pythonPackages.iso8601
      pythonPackages.pyasn1
      pythonPackages.pytest_29
      pythonPackages.py
      pythonPackages.hypothesis
      pythonPackages.pytz
    ];

    propagatedBuildInputs = [
      idna2_5

      pythonPackages.six
      pythonPackages.ipaddress
      pythonPackages.pyasn1
      pythonPackages.cffi
      pythonPackages.pyasn1-modules
      pythonPackages.pytz
      pythonPackages.enum34
    ];
  };

output

creating build/bdist.linux-x86_64/wheel/cryptography-1.9.dist-info/WHEEL
installing
/tmp/nix-build-python2.7-cryptography-1.9.drv-0/cryptography-1.9/dist /tmp/nix-build-python2.7-cryptography-1.9.drv-0/cryptography-1.9
Processing ./cryptography-1.9-cp27-cp27mu-linux_x86_64.whl
Collecting idna>=2.1 (from cryptography==1.9)
  Could not find a version that satisfies the requirement idna>=2.1 (from cryptography==1.9) (from versions: )
No matching distribution found for idna>=2.1 (from cryptography==1.9)
builder for ‘/nix/store/j5vk9qa3frfm3mhgiciha3cr8v34y7q7-python2.7-cryptography-1.9.drv’ failed with exit code 1
cannot build derivation ‘/nix/store/nwwccbw2x7y1fksafcfyc62m2cpnpbxc-python-2.7.13-env.drv’: 1 dependencies couldn't be built
cannot build derivation ‘/nix/store/j11brfff2wp05djypqkrp807py5yamj3-docker-layer-s4-common-image.drv’: 1 dependencies couldn't be built
cannot build derivation ‘/nix/store/zvwd87zfzmz4im604faxh3kb5k8pigkp-docker-image-s4-common-image.tar.gz.drv’: 1 dependencies couldn't be built
error: build of ‘/nix/store/zvwd87zfzmz4im604faxh3kb5k8pigkp-docker-image-s4-common-image.tar.gz.drv’ failed