pythonPackages.distributed: 1.15.1 -> 1.22.1

The github repository was downloaded instead of the pypi repository
for testing (needed `conftest.py`). Major work was done on the
underlying dependencies to make distributed work on python 2.7,
3+. Note that the test **do** take a significant amount of time (10-15
minutes).

 - moved to `python-modules`
 - compatible with 2.7, 3+
 - all tests pass (previously tests were not run)

pkgs/development/python-modules/distributed/default.nix

@@ -0,0 +1,59 @@
+{ lib
+, buildPythonPackage
+, fetchFromGitHub
+, pytest
+, pytest-repeat
+, pytest-faulthandler
+, pytest-timeout
+, mock
+, joblib
+, click
+, cloudpickle
+, dask
+, msgpack
+, psutil
+, six
+, sortedcontainers
+, tblib
+, toolz
+, tornado
+, zict
+, pyyaml
+, pythonOlder
+, futures
+, singledispatch
+}:
+
+buildPythonPackage rec {
+  pname = "distributed";
+  version = "1.22.1";
+
+  # get full repository need conftest.py to run tests
+  src = fetchFromGitHub {
+    owner = "dask";
+    repo = pname;
+    rev = version;
+    sha256 = "0xvx55rhbhlyys3kjndihwq6y6260qzy9mr3miclh5qddaiw2d5z";
+  };
+
+  checkInputs = [ pytest pytest-repeat pytest-faulthandler pytest-timeout mock joblib ];
+  propagatedBuildInputs = [
+      click cloudpickle dask msgpack psutil six
+      sortedcontainers tblib toolz tornado zict pyyaml
+  ] ++ lib.optional (pythonOlder "3.2") [ futures ]
+    ++ lib.optional (pythonOlder "3.4") [ singledispatch ];
+
+  # tests take about 10-15 minutes
+  # ignore 5 cli tests out of 1000 total tests that fail due to subprocesses
+  # these tests are not critical to the library (only the cli)
+  checkPhase = ''
+    py.test distributed -m "not avoid-travis" -r s --timeout-method=thread --timeout=0 --durations=20 --ignore="distributed/cli/tests"
+  '';
+
+  meta = {
+    description = "Distributed computation in Python.";
+    homepage = http://distributed.readthedocs.io/en/latest/;
+    license = lib.licenses.bsd3;
+    maintainers = with lib.maintainers; [ teh costrouc ];
+  };
+}