Getting same error with flair 0.4.3 and torch 1.2.0
System Cuda version
(py36) ➜  question_classifier_new_test nvcc --version
nvcc: NVIDIA (R) Cuda compiler driver
Copyright (c) 2005-2018 NVIDIA Corporation
Built on Sat_Aug_25_21:08:01_CDT_2018
Cuda compilation tools, release 10.0, V10.0.130

Pytorch Cuda version
Python 3.6.9 |Anaconda, Inc.| (default, Jul 30 2019, 19:07:31) 
[GCC 7.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import torch 
>>> torch.version.cuda
'10.0.130'

I was working the other time, and now its not. anything missing.
version 1.1.0 works fine but in 1.2.0, GRU and LSTM are removed to add torchscript support, refer link https://pytorch.org/docs/stable/_modules/torch/nn/modules/rnn.html 11