spyder: add patch fix startup error

Upstream clears out all sys.path entries that come from PYTHONPATH,
which completely breaks Nixpkgs packaging. Patch out that code to fix
running spyder.

Before:

$ spyder
Traceback (most recent call last):
File "/nix/store/icbklw22yrzy7s8k2ai8chkhrvna8pxr-python3.10-spyder-5.4.0/bin/..spyder-wrapped-wrapped", line 6, in <module>
from spyder.app.start import main
File "/nix/store/icbklw22yrzy7s8k2ai8chkhrvna8pxr-python3.10-spyder-5.4.0/lib/python3.10/site-packages/spyder/app/start.py", line 42, in <module>
import zmq
ModuleNotFoundError: No module named 'zmq'
(exit with error code 1)

After:

$ spyder
(succeeds startup)

Note that once the GUI is up, it complains (inside GUI) that we've got
wrong version of 2 deps and
"ModuleNotFoundError: No module named 'spyder_kernels'".

Fixes https://github.com/NixOS/nixpkgs/issues/208567

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

···
     hash = "sha256-kQBOYRXhjz+OQk7Vlxb/UKiDi92mA8ialsFQ+QzqhlE=";
   };
 
+  patches = [
+    ./dont-clear-pythonpath.patch
+  ];
+
   nativeBuildInputs = [
     pyqtwebengine.wrapQtAppsHook
   ];

pkgs/development/python-modules/spyder/dont-clear-pythonpath.patch

···
+Don't remove sys.path entries that come from PYTHONPATH, or else the app cannot
+be used in Nixpkgs.
+
+Author: Bjørn Forsman <[e-mail]>
+diff -uNr spyder-5.4.0.orig/spyder/app/start.py spyder-5.4.0/spyder/app/start.py
+--- spyder-5.4.0.orig/spyder/app/start.py	2022-08-30 02:02:28.000000000 +0200
++++ spyder-5.4.0/spyder/app/start.py	2023-01-02 11:38:28.138744879 +0100
+@@ -6,16 +6,8 @@
+ # (see spyder/__init__.py for details)
+ # -----------------------------------------------------------------------------
+ 
+-# Remove PYTHONPATH paths from sys.path before other imports to protect against
+-# shadowed standard libraries.
+ import os
+ import sys
+-if os.environ.get('PYTHONPATH'):
+-    for path in os.environ['PYTHONPATH'].split(os.pathsep):
+-        try:
+-            sys.path.remove(path.rstrip(os.sep))
+-        except ValueError:
+-            pass
+ 
+ # Standard library imports
+ import ctypes