mod_python: Avoid that git is called to generate a version

This failed when building mod_python and resulted in a broken
value being included in the file "version.py".

pkgs/servers/http/apache-modules/mod_python/default.nix

@@ -10,6 +10,12 @@ stdenv.mkDerivation rec {
 
   patches = [ ./install.patch ];
 
+  postPatch = ''
+    substituteInPlace dist/version.sh \
+        --replace 'GIT=`git describe --always`' "" \
+        --replace '-$GIT' ""
+  '';
+
   preInstall = ''
     installFlags="LIBEXECDIR=$out/modules $installFlags"
     mkdir -p $out/modules $out/bin