use torch

ml-agents/mlagents/trainers/settings.py

     threaded: bool = True
     self_play: Optional[SelfPlaySettings] = None
     behavioral_cloning: Optional[BehavioralCloningSettings] = None
-    framework: FrameworkType = FrameworkType.TENSORFLOW
+    framework: FrameworkType = FrameworkType.PYTORCH
 
     cattr.register_structure_hook(
         Dict[RewardSignalType, RewardSignalSettings], RewardSignalSettings.structure

ml-agents/setup.py

         # We don't actually need six, but tensorflow does, and pip seems
         # to get confused and install the wrong version.
         "six>=1.12.0",
+        "torch>=1.5.0",
     ],
     python_requires=">=3.6.1",
     entry_points={