Catch symlink failure on Windows

[del-zhenwu]

Signed-off-by: del-zhenwu dele.zhenwu@gmail.com

Thanks for your contribution and we appreciate it a lot. The following instructions would make your pull request more healthy and more easily get feedback. If you do not understand some items, don't worry, just make the pull request and seek help from maintainers.

Motivation

Fix #6480

Modification

Try to catch the exception raised by os.symlink on Windows

BC-breaking (Optional)

Does the modification introduce changes that break the backward-compatibility of the downstream repos?
If so, please describe how it breaks the compatibility and how the downstream projects should modify their code to keep compatibility with this PR.

Use cases (Optional)

If this PR introduces a new feature, it is better to list some use cases here, and update the documentation.

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects, like MMDet or MMCls.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #6482 (7210c39) into dev-v2.19.0 (a7a16af) will increase coverage by 0.04%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           dev-v2.19.0    #6482      +/-   ##
===============================================
+ Coverage        62.02%   62.06%   +0.04%     
===============================================
  Files              319      319              
  Lines            25340    25341       +1     
  Branches          4193     4193              
===============================================
+ Hits             15717    15729      +12     
+ Misses            8795     8782      -13     
- Partials           828      830       +2     

Flag	Coverage Δ
unittests	62.04% <ø> (+0.04%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
mmdet/core/bbox/assigners/max_iou_assigner.py	72.36% <0.00%> (-1.32%)	⬇️
mmdet/core/bbox/samplers/ohem_sampler.py	84.21% <0.00%> (+0.42%)	⬆️
mmdet/models/dense_heads/corner_head.py	69.46% <0.00%> (+1.40%)	⬆️
mmdet/models/dense_heads/base_dense_head.py	91.22% <0.00%> (+1.75%)	⬆️
mmdet/models/detectors/cornernet.py	100.00% <0.00%> (+5.12%)	⬆️
mmdet/core/bbox/samplers/random_sampler.py	80.55% <0.00%> (+5.55%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a7a16af...7210c39. Read the comment docs.

[RangiLyu]

Thanks for your contribution! Please sign the CLA first.

[RangiLyu]

Hi, the lint failed. Please install pre-commit and then run pre-commit run --all-files to fix.

[del-zhenwu]

The result of unit test seems to be is unstable.

[RangiLyu]

The result of unit test seems to be is unstable.

It seems the reason of the latest version of MMCV. open-mmlab/mmcv#1418 This PR breaked the pvt unit tests.
Sorry for that. We will solve that problem asap.

[hhaAndroid]

Logic should be:

if 'develop' in sys.argv :
  if platform.system() == 'Windows': 
      mode='copy'
  else:
     mode='sylink'

[del-zhenwu]

I will make a fix

[RangiLyu]

CI has been fixed in 2.18.1. Please pull master and rerun the tests.