On a server without python3, python_grpclib_library fails with /usr/bin/env: 'python3': No such file or directory

[blockjon-dd]

Issue Description

I'm seeing the following error:

/usr/bin/env: 'python3': No such file or directory

when I try to build python_grpclib_library where the host does not have python.

Repro

To repro, make sure you run this on a machine where python3 is not installed globally.

Log Output

ERROR: /workspace/build/x/x/protos/public/payment/v0/BUILD.bazel:17:13: Compiling protoc outputs for grpclib_plugin plugin on target @@//protos/public/payment/v0:payment_v0_go_proto_python_grpc_compile_pb failed: (Exit 1): bash failed: error executing ProtoCompile command (from target //protos/public/payment/v0:payment_v0_go_proto_python_grpc_compile_pb) /bin/bash -c ... (remaining 8 arguments skipped)
Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
/usr/bin/env: 'python3': No such file or directory
--grpclib_plugin_out: protoc-gen-grpclib_plugin: Plugin failed with status code 127.

rules_proto_grpc Version

5.0.1

Bazel Version

7.4.0

OS

Debian bookworm

Link to Demo Repo

No response

MODULE.bazel or WORKSPACE Content

bazel_dep(name = "rules_python", version = "0.37.2")
bazel_dep(name = "protobuf", version = "29.1", repo_name = "com_google_protobuf")
bazel_dep(name = "rules_proto_grpc", version = "5.0.1")
bazel_dep(name = "rules_proto_grpc_python", version = "5.0.1")
bazel_dep(name = "rules_proto", version = "6.0.2")

python = use_extension("@rules_python//python/extensions:python.bzl", "python")
python.toolchain(python_version = "3.11")

BUILD Content

load("@rules_proto//proto:defs.bzl", "proto_library")
load("@rules_proto_grpc_python//:defs.bzl", "python_grpclib_library")

proto_library(
    name = "proto",
    srcs = [
        "addressbook.proto",
    ],
)

python_grpclib_library(
    name = "grpc_lib",
    protos = [
        ":proto",
    ],
)

Proto Content

syntax = "proto3";

package demo;

message Person {
  string name = 1;
  int32 id = 2;
  string email = 3;
}

Any Other Content