Add poetry2nix environment

.gitignore

@@ -6,4 +6,5 @@ build
 dist
 .vscode/launch.json
 .vscode/settings.json
-tests/orb_tomog_regression_tests.py
\ No newline at end of file
+tests/orb_tomog_regression_tests.py
+/env

env.nix

+# Build with
+#
+#     nix-build env.nix -o env
+#
+# VSCode will see the generated ./env as a virtualenv and offer it as an
+# interpreter in the ‘Python: Select Interpreter’ command.
+#
+# To run Python with all dependencies available, use the wrapper script
+# env/bin/python.
+
+{ nixpkgs ? <nixpkgs>, pkgs ? import nixpkgs {} }:
+
+with pkgs;
+
+poetry2nix.mkPoetryEnv {
+  projectDir = ./.;
+  preferWheels = true;
+  overrides = poetry2nix.overrides.withDefaults (self: super: {
+    # We need to explicityly specify the dependency on the plotting backend.
+    # Use tkinter for simplicity.
+    matplotlib = super.matplotlib.overridePythonAttrs (attrs: {
+      propagatedBuildInputs = attrs.propagatedBuildInputs ++ [
+        self.tkinter
+      ];
+    });
+  });
+}