[BUG] module not find when run from the same folder as the shared object

[tdegeus]

Issue description

I'm compiling a Python module, and running a Python code from the same folder as the shared object. This mostly works, but sometimes fails with no apparent reason with

ModuleNotFoundError: No module named 'mymodule'

Reproducible example code

I put a minimal reproducible example with CI in a clean environment here. As can be observed, it fails in this case on Windows. Just to list the example here as well:

main.cpp

#include <vector>
#include <pybind11/pybind11.h>
#include <pybind11/stl.h>

namespace py = pybind11;

template <class T>
inline T foo(T& arg)
{
    T ret = arg;

    for (auto& i : ret) {
        i *= 2;
    }

    return ret;
}

PYBIND11_MODULE(mymodule, m)
{
    m.doc() = "Module description";
    m.def("foo", &foo<std::vector<int>>, "Function description", py::arg("arg"));
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.18..3.20)

project(mymodule)

find_package(Python REQUIRED COMPONENTS Interpreter Development NumPy)
find_package(pybind11 REQUIRED CONFIG)

pybind11_add_module(mymodule main.cpp)
target_link_libraries(mymodule PUBLIC pybind11::module Python::NumPy)

target_compile_definitions(mymodule PRIVATE VERSION_INFO=0.1.0)

example.py

import mymodule
import numpy as np

A = (np.random.random([100]) * 100).astype(np.uint64)
assert np.all(A * 2 == mymodule.foo(A))

Build instructions

cmake -Bbuild -DPython_EXECUTABLE=`which python`
cd build
cmake --build .
cp ../example.py .
python example.py