libxml2,libxslt: fix pythonSupport=false override

pkgs/development/libraries/libxslt/default.nix

@@ -3,9 +3,6 @@
 , pythonSupport ? stdenv.buildPlatform == stdenv.hostPlatform
 }:
 
-assert pythonSupport -> python != null;
-assert pythonSupport -> libxml2.pythonSupport;
-
 with stdenv.lib;
 
 stdenv.mkDerivation rec {
@@ -53,5 +50,6 @@ stdenv.mkDerivation rec {
     license = licenses.mit;
     platforms = platforms.all;
     maintainers = [ maintainers.eelco ];
+    broken = !(pythonSupport -> libxml2.pythonSupport); # see #73102 for why this is not an assert
   };
 }