Emit warning from deprecated torch function signatures (#32009)
Summary:
Continuation of https://github.com/pytorch/pytorch/issues/31514, fixes https://github.com/pytorch/pytorch/issues/28430
Pull Request resolved: https://github.com/pytorch/pytorch/pull/32009
Test Plan:
I verified that the deprecation warnings only occur once on a relevant workflow. Built with:
```
buck build mode/opt //vision/fair/detectron2/tools:train_net
```
Ran with:
```
DETECTRON2_ENV_MODULE=detectron2.fb.env ~/local/train_net.par --config-file configs/quick_schedules/retinanet_R_50_FPN_instant_test.yaml --num-gpus 1 SOLVER.IMS_PER_BATCH 2
```
Inspected log:
```
[01/14 07:28:13 d2.engine.train_loop]: Starting training from iteration 0
buck-out/opt/gen/caffe2/generate-code=python_variable_methods.cpp/python_variable_methods.cpp:1299: UserWarning: This overload of add is deprecated:
add(Number alpha, Tensor other)
Consider using one of the following signatures instead:
add(Tensor other, Number alpha)
buck-out/opt/gen/caffe2/generate-code=python_variable_methods.cpp/python_variable_methods.cpp:1334: UserWarning: This overload of add_ is deprecated:
add_(Number alpha, Tensor other)
Consider using one of the following signatures instead:
add_(Tensor other, Number alpha)
[01/14 07:28:25 d2.utils.events]: eta: 0:00:10 iter: 19 total_loss: 1.699 loss_cls: 1.185 loss_box_reg: 0.501 time: 0.5020 data_time: 0.0224 lr: 0.000100 max_mem: 3722M
[01/14 07:28:35 fvcore.common.checkpoint]: Saving checkpoint to ./output/model_final.pth
```
Differential Revision: D19373523
Pulled By: ezyang
fbshipit-source-id: 75756de129645501f43ecc4e3bf8cc0f78c40b90
