No module named 'densepose'

## Instructions To Reproduce the 🐛 Bug:
1. installing the following using pip in collab notebook :
- torch==1.10.1+cu102 torchvision==0.11.2+cu102 torchaudio==0.10.1 -f https://download.pytorch.org/whl/torch_stable.html
- detectron2==0.6 -f \ https://dl.fbaipublicfiles.com/detectron2/wheels/cu102/torch1.10/index.html
- git+https://github.com/facebookresearch/detectron2@main#subdirectory=projects/DensePose

2. after, restarting runtime I run:
!python ./apply_net.py dump densepose_rcnn_R_101_FPN_DL_s1x.yaml \
https://dl.fbaipublicfiles.com/densepose/densepose_rcnn_R_101_FPN_DL_s1x/165712116/model_final_844d15.pkl \
./Tejrab/200404.png --output ./dump/200404.pkl -v

## Expected behavior:

pkl file of the png image

## Error
1. Traceback (most recent call last):
File "./apply_net.py", line 19, in
from densepose import add_densepose_config
ModuleNotFoundError: No module named 'densepose'

after installing densepose this error occured
2. ERROR: Command errored out with exit status 1: /usr/bin/python3 -u -c 'import io, os, sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-g43tc9ql/detectron2_0a570229969d47198f45a267ccc78493/setup.py'"'"'; __file__='"'"'/tmp/pip-install-g43tc9ql/detectron2_0a570229969d47198f45a267ccc78493/setup.py'"'"';f = getattr(tokenize, '"'"'open'"'"', open)(__file__) if os.path.exists(__file__) else io.StringIO('"'"'from setuptools import setup; setup()'"'"');code = f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record /tmp/pip-record-px39tp0q/install-record.txt --single-version-externally-managed --compile --install-headers /usr/local/include/python3.7/detectron2 Check the logs for full command output.

## PS
a new commit to apply_net.py has been added by authors
https://github.com/facebookresearch/detectron2/commit/c54429b60a64736c8b62002c5729eb818835f745
**could it be the reason ?**

Start by reproducing the listed Colab installation commands and the apply_net.py invocation, then inspect the import at apply_net.py line 19. Compare the reported behavior with commit c54429b60a64736c8b62002c5729eb818835f745 and the installation logs. Done means the environment imports densepose and the command produces the expected pkl file.

Written by the indexing model from the issue text.