pythonPackages.pyqtwebengine: Apply qt5.14 patch only if needed

Since we now use qt5.15 in all python modules (defaulting to the same
qt5 used in all-packages.nix), That patch is not required, but it will
be needed if qt5.14 is used if pythonInterpreters is overridden, which
is likely to happen like it happend to qutebrowser for instance. See:
https://github.com/NixOS/nixpkgs/pull/99956/commits/2667af4062ef0710b486fbae3108e0141aecb0fc

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

@@ -7,6 +7,10 @@ let
 
   inherit (pythonPackages) buildPythonPackage python isPy3k pyqt5 enum34;
   inherit (pyqt5) sip;
+  # source: https://www.riverbankcomputing.com/pipermail/pyqt/2020-June/042985.html
+  patches = lib.optional (lib.hasPrefix "5.14" pyqt5.version)
+    [ ./fix-build-with-qt-514.patch ]
+  ;
 
 in buildPythonPackage rec {
   pname = "PyQtWebEngine";
@@ -18,10 +22,7 @@ in buildPythonPackage rec {
     sha256 = "0xdzhl07x3mzfnr5cf4d640168vxi7fyl0fz1pvpbgs0irl14237";
   };
 
-  patches = [
-    # source: https://www.riverbankcomputing.com/pipermail/pyqt/2020-June/042985.html
-    ./fix-build-with-qt-514.patch
-  ];
+  inherit patches;
 
   outputs = [ "out" "dev" ];