ValueError: bad value(s) in fds_to_keep, when attemping DDP
I can't get DDP working without getting the following error:
Traceback (most recent call last):
  File "train.py", line 86, in <module>
    main(config)
  File "train.py", line 41, in main
    trainer.fit(model)
  File "/home/ubuntu/anaconda3/envs/pytorch_p36/lib/python3.6/site-packages/pytorch_lightning/trainer/trainer.py", line 343, in fit
    mp.spawn(self.ddp_train, nprocs=self.num_gpus, args=(model,))
  File "/home/ubuntu/anaconda3/envs/pytorch_p36/lib/python3.6/site-packages/torch/multiprocessing/spawn.py", line 162, in spawn
    process.start()
  File "/home/ubuntu/anaconda3/envs/pytorch_p36/lib/python3.6/multiprocessing/process.py", line 105, in start
    self._popen = self._Popen(self)
  File "/home/ubuntu/anaconda3/envs/pytorch_p36/lib/python3.6/multiprocessing/context.py", line 284, in _Popen
    return Popen(process_obj)
  File "/home/ubuntu/anaconda3/envs/pytorch_p36/lib/python3.6/multiprocessing/popen_spawn_posix.py", line 32, in __init__
    super().__init__(process_obj)
  File "/home/ubuntu/anaconda3/envs/pytorch_p36/lib/python3.6/multiprocessing/popen_fork.py", line 19, in __init__
    self._launch(process_obj)
  File "/home/ubuntu/anaconda3/envs/pytorch_p36/lib/python3.6/multiprocessing/popen_spawn_posix.py", line 59, in _launch
    cmd, self._fds)
  File "/home/ubuntu/anaconda3/envs/pytorch_p36/lib/python3.6/multiprocessing/util.py", line 417, in spawnv_passfds
    False, False, None)
ValueError: bad value(s) in fds_to_keep
What I have tried and that didn't work:

Python 3.7
Python 3.6
pytorch 1.1.0
pytorch 1.2.0
Downgrading "scikit-learn" which had helped in unrelated projects according to results on Google
Lightning 0.5.3.2
Lightning master version
Lightning 0.5.2.1
CUDA 9.0
CUDA 9.2
CUDA 10.0
Tried removing visdom from the project

The error occurs on two servers I tried on, one with 4 Titan X cards and one with 8 Tesla V100 running Ubuntu 18.04.3 LTS.
I suspect that something in my model is triggering it and would appreciate ideas. I can not share the source code though. The model works in dp and single gpu mode.