python: add python.withPackages function

Fixes #15801

pkgs/development/interpreters/python/2.6/default.nix

···
 { stdenv, fetchurl, zlib ? null, zlibSupport ? true, bzip2, includeModules ? false
-, sqlite, tcl, tk, xlibsWrapper, openssl, readline, db, ncurses, gdbm, self, callPackage }:
+, sqlite, tcl, tk, xlibsWrapper, openssl, readline, db, ncurses, gdbm, self, callPackage
+, python26Packages }:
 
 assert zlibSupport -> zlib != null;
 
···
       isPy2 = true;
       isPy26 = true;
       buildEnv = callPackage ../wrapper.nix { python = self; };
+      withPackages = import ../with-packages.nix { inherit buildEnv; pythonPackages = python26Packages; };
       libPrefix = "python${majorVersion}";
       executable = libPrefix;
       sitePackages = "lib/${libPrefix}/site-packages";

pkgs/development/interpreters/python/2.7/default.nix

···
-{ stdenv, fetchurl, self, callPackage
+{ stdenv, fetchurl, self, callPackage, python27Packages
 , bzip2, openssl, gettext
 
 , includeModules ? false
···
       isPy2 = true;
       isPy27 = true;
       buildEnv = callPackage ../wrapper.nix { python = self; };
+      withPackages = import ../with-packages.nix { inherit buildEnv; pythonPackages = python27Packages; };
       libPrefix = "python${majorVersion}";
       executable = libPrefix;
       sitePackages = "lib/${libPrefix}/site-packages";

pkgs/development/interpreters/python/3.3/default.nix

···
 , zlib
 , callPackage
 , self
+, python33Packages
 }:
 
 assert readline != null -> ncurses != null;
···
     libPrefix = "python${majorVersion}";
     executable = "python3.3m";
     buildEnv = callPackage ../wrapper.nix { python = self; };
+    withPackages = import ../with-packages.nix { inherit buildEnv; pythonPackages = python33Packages; };
     isPy3 = true;
     isPy33 = true;
     is_py3k = true;  # deprecated

pkgs/development/interpreters/python/3.4/default.nix

···
 , zlib
 , callPackage
 , self
+, python34Packages
 
 , CF, configd
 }:
···
     libPrefix = "python${majorVersion}";
     executable = "python3.4m";
     buildEnv = callPackage ../wrapper.nix { python = self; };
+    withPackages = import ../with-packages.nix { inherit buildEnv; pythonPackages = python34Packages; };
     isPy3 = true;
     isPy34 = true;
     is_py3k = true;  # deprecated

pkgs/development/interpreters/python/3.5/default.nix

···
 , zlib
 , callPackage
 , self
+, python35Packages
 
 , CF, configd
 }:
···
     libPrefix = "python${majorVersion}";
     executable = "python${majorVersion}m";
     buildEnv = callPackage ../wrapper.nix { python = self; };
+    withPackages = import ../with-packages.nix { inherit buildEnv; pythonPackages = python35Packages; };
     isPy3 = true;
     isPy35 = true;
     is_py3k = true;  # deprecated

pkgs/development/interpreters/python/with-packages.nix

···
+{ buildEnv, pythonPackages }:
+
+f: let packages = f pythonPackages; in buildEnv.override { extraLibs = packages; }