No module named ipykernel

[domarps]

🐛 Bug

Error when running demo/Mask_R-CNN_demo.ipynb with jupyter:

To Reproduce

Steps to reproduce the behavior:

1. Follow the Option 1 of installation as mentioned in docs
2. jupyter lab --allow-root
3. From the list of kernels, choose Environment (conda_maskrcnn_benchmark)
4. Run cell : from maskrcnn_benchmark.config import cfg

[W 00:28:50.460 LabApp] Could not determine jupyterlab build status without nodejs
[I 00:28:52.230 LabApp] Kernel started: eacbf034-8e83-497a-bc65-a03b6a7e0aba
[I 00:28:52.240 LabApp] Kernel started: d43ec820-bdf7-4510-a5af-674a1ee0f55e
/home/ubuntu/anaconda3/envs/maskrcnn_benchmark/bin/python: No module named ipykernel
/home/ubuntu/anaconda3/envs/maskrcnn_benchmark/bin/python: No module named ipykernel
[I 00:28:55.232 LabApp] KernelRestarter: restarting kernel (1/5), new random ports
[I 00:28:55.239 LabApp] KernelRestarter: restarting kernel (1/5), new random ports

Expected behavior

Cell executes without displaying 'No Kernel!'

Environment

PyTorch version: 1.1.0.dev20190430
Is debug build: No
CUDA used to build PyTorch: 9.0.176

OS: Ubuntu 16.04.5 LTS
GCC version: (Ubuntu 5.4.0-6ubuntu1~16.04.10) 5.4.0 20160609
CMake version: version 3.5.1

Python version: 3.7
Is CUDA available: Yes
CUDA runtime version: 9.0.176
GPU models and configuration: GPU 0: Tesla V100-SXM2-16GB
Nvidia driver version: 396.44
cuDNN version: Could not collect

Versions of relevant libraries:
[pip3] numpy==1.15.1
[conda] blas                      1.0                         mkl
[conda] mkl                       2019.3                      199
[conda] mkl_fft                   1.0.12           py37ha843d7b_0
[conda] mkl_random                1.0.2            py37hd81dba3_0
[conda] pytorch                   1.0.1           py3.7_cuda9.0.176_cudnn7.4.2_2    pytorch
[conda] pytorch-nightly           1.1.0.dev20190430 py3.7_cuda9.0.176_cudnn7.5.1_0    pytorch
[conda] torchvision               0.2.2                      py_3    pytorch

Additional context

Adding the following line after installation fixes the problem (Ref : jupyter/notebook#1558):

conda install ipykernel