GAN Manual optimization not working after 1.0.7
🐛 Bug
I have a GAN model and as of 1.0.7 it no longer trains correctly. I've tried to troubleshoot the issue to the best of my ability but I have no idea what's causing the problem.
Please reproduce using the BoringModel

https://colab.research.google.com/gist/import-antigravity/0730243bb11b56031110fd6aa7d58971/the-boringmodel.ipynb
To Reproduce
See boringmodel above^^^
Expected behavior
Using the colab notebook switch between version 1.0.6 and 1.0.7 to see the bug. For 1.0.6 after training a few epochs it's clear the GAN is beginning to converge, for 1.0.7 it just makes noise.
Environment

PyTorch Version (e.g., 1.0): 1.0.7
OS (e.g., Linux): macOS, Linux
How you installed PyTorch (conda, pip, source): conda
Build command you used (if compiling from source): n/a
Python version: 3.8
CUDA/cuDNN version: N/A
GPU models and configuration: N/A
Any other relevant information: N/A