workaround: depend on rules_python

I think I'll need eyes from Xudong to understand the failure mode

MODULE.bazel

diff --git a/MODULE.bazel b/MODULE.bazel
index ff37643..a701b57 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -12,6 +12,14 @@
 bazel_dep(name = "bazel_features", version = "1.2.0")
 bazel_dep(name = "platforms", version = "0.0.8")
 
+# FIXME: this should not be needed.
+# Something seems wrong with toolchain registration otherwise.
+# ERROR: com.google.devtools.build.lib.packages.BuildFileNotFoundException:
+# no such package '@@[unknown repo 'rules_python' requested from @@rules_proto~override]//python/proto':
+# The repository '@@[unknown repo 'rules_python' requested from @@rules_proto~override]' could not be resolved:
+# No repository visible as '@rules_python' from repository '@@rules_proto~override'
+bazel_dep(name = "rules_python", version = "0.31.0")
+
 # Dependencies needed in tests
 bazel_dep(name = "stardoc", version = "0.5.6", dev_dependency = True, repo_name = "io_bazel_stardoc")
 bazel_dep(name = "rules_cc", version = "0.0.1", dev_dependency = True)