Add preInstall ot buildPythonPackage (postInstall already existed) to allow selenium to work properly again.

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

@@ -37,6 +37,7 @@
       runHook postCheck
     ''
 
+, preInstall ? ""
 , postInstall ? ""
 
 , ... } @ attrs:
@@ -63,7 +64,7 @@ python.stdenv.mkDerivation (attrs // {
     ${preConfigure}
   '';
 
-  installPhase = ''
+  installPhase = preInstall + ''
     mkdir -p "$out/lib/${python.libPrefix}/site-packages"
 
     echo "installing \`${name}' with \`easy_install'..."

pkgs/top-level/python-packages.nix

@@ -2599,7 +2599,6 @@ let pythonPackages = python.modules // rec {
           sha256 = "1wif9r6307qhlcp2zbg6n05yvxxn9ppkxh8gpsplcbyh22zi7bcd";
         };
 
-      preInstallPhases = "preInstall";
       preInstall = ''
         cp ${x_ignore_nofocus}/* .
         sed -i 's|dlopen(library,|dlopen("libX11.so.6",|' x_ignore_nofocus.c