Added nix shell doodas

.envrc

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+use nix
+layout python3

default.nix

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+with import <nixpkgs> { };
+
+let
+  pythonPackages = python3Packages;
+in pkgs.mkShell rec {
+  name = "impurePythonEnv";
+  venvDir = "./.venv";
+  buildInputs = [
+    # A Python interpreter including the 'venv' module is required to bootstrap
+    # the environment.
+    pythonPackages.python
+    pylint
+    black
+    python311Packages.future
+    qgis
+    vscode
+    xorg.libxcb
+    qgis
+    qt5.full
+    qtcreator
+    python3
+    python3Packages.pyqt5
+    python3Packages.gdal
+    python3Packages.pytest
+
+    # This executes some shell code to initialize a venv in $venvDir before
+    # dropping into the shell
+
+  ];
+
+  # Run this command, only after creating the virtual environment
+  postVenvCreation = ''
+    unset SOURCE_DATE_EPOCH
+    pip install -r requirements.txt
+  '';
+
+  shellHook = ''
+    export PYTHONPATH=$PYTHONPATH:`which qgis`/../../share/qgis/python
+    export QT_QPA_PLATFORM=offscreen
+  '';
+
+  # Now we can execute any commands within the virtual environment.
+  # This is optional and can be left out to run pip manually.
+  postShellHook = ''
+    # allow pip to install wheels
+    unset SOURCE_DATE_EPOCH
+  '';
+
+}