add discoverer for python

src/discoverers/python/default.nix

@@ -0,0 +1,35 @@
+{
+  dlib,
+  lib,
+  subsystem,
+}: let
+  l = lib // builtins;
+
+  discover = {tree}: let
+    subdirProjects =
+      l.flatten
+      (l.mapAttrsToList
+        (dirName: dir: discover {tree = dir;})
+        (tree.directories or {}));
+  in
+    # A directory is identified as a project only if it contains a Cargo.toml
+    # and a Cargo.lock.
+    if tree ? files."setup.py"
+    then
+      [
+        (dlib.construct.discoveredProject {
+          inherit subsystem;
+          relPath = tree.relPath;
+          name =
+            l.unsafeDiscardStringContext
+            (l.last
+              (l.splitString "/" (l.removeSuffix "/" "${tree.fullPath}")));
+          translators = ["pip-WIP"];
+          subsystemInfo.pythonAttr = "python3";
+        })
+      ]
+      ++ subdirProjects
+    else subdirProjects;
+in {
+  inherit discover;
+}