gan.py multi-gpu running problems
Running gan.py example with Trainer(ngpus=2) causes two types of error:

if Trainer(ngpus=2, distributed_backend='dp')

Exception has occurred: AttributeError
'NoneType' object has no attribute 'detach'
  File "/home/user/gan.py", line 146, in training_step
    self.discriminator(self.generated_imgs.detach()), fake)


if Trainer(ngpus=2, distributed_backend='ddp')


in ./lightling_logs one run creates two folders: version_0 and version_1
Exception caused:
File "/opt/miniconda3/envs/ctln-gan/lib/python3.7/site-packages/pytorch_lightning/callbacks/model_checkpoint.py", line 122, in _del_model
os.remove(filepath)
FileNotFoundError: [Errno 2] No such file or directory: '/home/user/pyproj/DCGAN/lightning_logs/version_1/checkpoints/epoch=0.ckpt'

it seems that each subprocess tries to create its own checkpoints and delete not ctrated one.
Environment version:
python 3.7.5
pytorch 1.4.0
pytorch-lightning 0.7.1