dependencies: Add futures as a dependency of Gunicorn.

Gunicorn needs futures on Python 2 when used with multiple threads per worker.

This is addressing issue  #3995.

pkgs/python-packages-overrides.nix

@@ -1,151 +1,159 b''
 # Overrides for the generated python-packages.nix
 #
 # This function is intended to be used as an extension to the generated file
 # python-packages.nix. The main objective is to add needed dependencies of C
 # libraries and tweak the build instructions where needed.
 
 { pkgs, basePythonPackages }:
 
 let
   sed = "sed -i";
 in
 
 self: super: {
 
   gnureadline = super.gnureadline.override (attrs: {
     buildInputs = attrs.buildInputs ++ [
       pkgs.ncurses
     ];
     patchPhase = ''
       substituteInPlace setup.py --replace "/bin/bash" "${pkgs.bash}/bin/bash"
     '';
   });
 
+  gunicorn = super.gunicorn.override (attrs: {
+    propagatedBuildInputs = attrs.propagatedBuildInputs ++ [
+      # johbo: futures is needed as long as we are on Python 2, otherwise
+      # gunicorn explodes if used with multiple threads per worker.
+      self.futures
+    ];
+  });
+
   kombu = super.kombu.override (attrs: {
     # The current version of kombu needs some patching to work with the
     # other libs. Should be removed once we update celery and kombu.
     patches = [
       ./patch-kombu-py-2-7-11.diff
       ./patch-kombu-msgpack.diff
     ];
   });
 
   lxml = super.lxml.override (attrs: {
     buildInputs = with self; [
       pkgs.libxml2
       pkgs.libxslt
     ];
   });
 
   MySQL-python = super.MySQL-python.override (attrs: {
     buildInputs = attrs.buildInputs ++ [
       pkgs.openssl
     ];
     propagatedBuildInputs = attrs.propagatedBuildInputs ++ [
       pkgs.mysql.lib
       pkgs.zlib
     ];
   });
 
   psutil = super.psutil.override (attrs: {
     buildInputs = attrs.buildInputs ++
       pkgs.lib.optional pkgs.stdenv.isDarwin pkgs.darwin.IOKit;
   });
 
   psycopg2 = super.psycopg2.override (attrs: {
     buildInputs = attrs.buildInputs ++
       pkgs.lib.optional pkgs.stdenv.isDarwin pkgs.openssl;
     propagatedBuildInputs = attrs.propagatedBuildInputs ++ [
       pkgs.postgresql
     ];
   });
 
   pycurl = super.pycurl.override (attrs: {
     propagatedBuildInputs = attrs.propagatedBuildInputs ++ [
       pkgs.curl
       pkgs.openssl
     ];
     preConfigure = ''
       substituteInPlace setup.py --replace '--static-libs' '--libs'
       export PYCURL_SSL_LIBRARY=openssl
     '';
   });
 
   Pylons = super.Pylons.override (attrs: {
     name = "Pylons-1.0.1-patch1";
     src = pkgs.fetchgit {
       url = "https://code.rhodecode.com/upstream/pylons";
       rev = "707354ee4261b9c10450404fc9852ccea4fd667d";
       sha256 = "b2763274c2780523a335f83a1df65be22ebe4ff413a7bc9e9288d23c1f62032e";
     };
   });
 
   pyramid = super.pyramid.override (attrs: {
     postFixup = ''
       wrapPythonPrograms
       # TODO: johbo: "wrapPython" adds this magic line which
       # confuses pserve.
       ${sed} '/import sys; sys.argv/d' $out/bin/.pserve-wrapped
     '';
   });
 
   Pyro4 = super.Pyro4.override (attrs: {
     # TODO: Was not able to generate this version, needs further
     # investigation.
     name = "Pyro4-4.35";
     src = pkgs.fetchurl {
       url = "https://pypi.python.org/packages/source/P/Pyro4/Pyro4-4.35.src.tar.gz";
       md5 = "cbe6cb855f086a0f092ca075005855f3";
     };
   });
 
   pysqlite = super.pysqlite.override (attrs: {
     propagatedBuildInputs = [
       pkgs.sqlite
     ];
   });
 
   pytest-runner = super.pytest-runner.override (attrs: {
     propagatedBuildInputs = [
       self.setuptools-scm
     ];
   });
 
   python-ldap = super.python-ldap.override (attrs: {
     propagatedBuildInputs = attrs.propagatedBuildInputs ++ [
       pkgs.cyrus_sasl
       pkgs.openldap
       pkgs.openssl
     ];
     NIX_CFLAGS_COMPILE = "-I${pkgs.cyrus_sasl}/include/sasl";
   });
 
   python-pam = super.python-pam.override (attrs:
     let
       includeLibPam = pkgs.stdenv.isLinux;
     in {
       # TODO: johbo: Move the option up into the default.nix, we should
       # include python-pam only on supported platforms.
       propagatedBuildInputs = attrs.propagatedBuildInputs ++
         pkgs.lib.optional includeLibPam [
           pkgs.pam
         ];
       # TODO: johbo: Check if this can be avoided, or transform into
       # a real patch
       patchPhase = pkgs.lib.optionals includeLibPam ''
         substituteInPlace pam.py \
           --replace 'find_library("pam")' '"${pkgs.pam}/lib/libpam.so.0"'
       '';
     });
 
   rhodecode-tools = super.rhodecode-tools.override (attrs: {
     patches = [
       ./patch-rhodecode-tools-setup.diff
     ];
   });
 
   # Avoid that setuptools is replaced, this leads to trouble
   # with buildPythonPackage.
   setuptools = basePythonPackages.setuptools;
 
 }