JIT not compatible with PyTorch/XLA
Tracing with JIT is not supported by TPUs. If `torch_xla` is detected in the environment, the `gelu_new` method won't be traced.

If tracing is done, the line:

```py
model = xm.send_cpu_data_to_device(model, xm.xla_device())
```
in `modeling_utils.py`

will raise:

```py
TypeError: can't pickle torch._C.ScriptFunction objects
```


the `# noqa F401` is necessary, otherwise, flake8 gives the following error:
```
src/transformers/activations.py:37:9: F401 'torch_xla' imported but unused
```
cc @jysohn23 