pyimport got stuck with deadlock

Hello,

I'm using PyCall v1.91.4 to import `rdkit.Chem` package from Python. It was working well until this Monday. The only change I made over the last weekend was to upgrade my scikit-learn package to 0.23.1 in Python. At first when I tried using `pyimport("rdkit.Chem")` in Julia on Monday, I got an error saying that `libmkl_intel_thread.dylib` was not loaded. After I did `conda install -c intel mkl`, even more strange issues occurred.
If I directly import Chem subpackage from rdkit, Julia will just get stuck with a deadlock
```
julia> Chem = pyimport("rdkit.Chem")
```
However, importing rdkit will not cause this issue.
```
julia> rdkit = pyimport("rdkit")
PyObject
```

The package itself doesn't seem to be problematic. When I imported it in Python, it was all good.
```
>>> import rdkit.Chem as Chem
>>> Chem.MolFromSmiles("C")

```

I've tried reconfiguring `ENV["PYTHON"] = my/path/to/correct/python` and then rebuild PyCall. But This didn't help. The `my/path/to/correct/python` was retrieved from using `which python`, so I think this is the correct path.
I even have tried completely reinstalling Julia v1.4.0 as well as wiping `~/.julia` folder but it didn't help either.

Empieza reproduciendo pyimport("rdkit.Chem") en PyCall con el entorno de Python indicado y compáralo después con pyimport("rdkit"), que no entra en deadlock. Investiga el cambio en el entorno de MKL/scikit-learn y la ruta de importación de PyCall; se considera terminado cuando la importación de Chem se completa sin quedarse bloqueada.

Escrito por el modelo de indexación a partir del texto del issue.