python.pkgs.tensorflow: add functools32 dependency

Now needed at runtime with the python2 build.

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

@@ -365,6 +365,7 @@ in buildPythonPackage {
   ] ++ lib.optionals (!isPy3k) [
     mock
     future
+    functools32
   ] ++ lib.optionals (pythonOlder "3.4") [
     backports_weakref enum34
   ] ++ lib.optionals withTensorboard [