[ci] Unpickling error for pretrained parameter loading

[frgfm]

🐛 Bug

The pretrained=True option on models cannot be tested by CI, since passing it produces a pickle error that cannot be reproduced locally.

To Reproduce

Steps to reproduce the behavior:

1. Running the pkg-test CI job on this commit

which produces:

Traceback (most recent call last):
  File "/home/circleci/repo/test/test_models.py", line 22, in test_resnet
    model = models.resnet(depth=18, pretrained=True, bin_classif=True).eval()
  File "/home/circleci/repo/pyronear/models/resnet.py", line 49, in resnet
    progress=progress)
  File "/home/circleci/repo/venv/lib/python3.6/site-packages/torch/hub.py", line 499, in load_state_dict_from_url
    return torch.load(cached_file, map_location=map_location)
  File "/home/circleci/repo/venv/lib/python3.6/site-packages/torch/serialization.py", line 426, in load
    return _load(f, map_location, pickle_module, **pickle_load_args)
  File "/home/circleci/repo/venv/lib/python3.6/site-packages/torch/serialization.py", line 603, in _load
    magic_number = pickle_module.load(f, **pickle_load_args)
_pickle.UnpicklingError: invalid load key, 'Y'.

Expected behavior

State dictionary loading should not produce errors.

Environment

Please copy and paste the output from our
environment collection script
(or fill out the checklist below manually).

You can get the script and run it with:

wget https://raw.githubusercontent.com/frgfm/PyroNear/master/pyronear/utils/collect_env.py
# For security purposes, please check the contents of collect_env.py before running it.
python collect_env.py

• PyTorch Version: 1.3.0
• Torchvision Version: 0.4.1a0+d94043a
• OS: Ubuntu 18.04
• How you installed PyTorch: conda
• Python version: 3.7
• CUDA/cuDNN version: CUDA 10.1.168 / cuDNN 7.6.2
• GPU models and configuration: GeForce GTX 1050 (driver: 430.50)

[frgfm]

This issue seems to have been fixed a while back, I'm not able to reproduce it anymore.
Closing for now, feel free to reopen if you encounter it!