[Fix] Deprecate the support for "python setup.py test"

[MengzhangLI]

Refer to open-mmlab/mmcv#1637 and open-mmlab/mmpose#1135.

[codecov]

Codecov Report

Merging #1201 (16224b1) into master (6c3e63e) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1201   +/-   ##
=======================================
  Coverage   90.10%   90.10%           
=======================================
  Files         126      126           
  Lines        7430     7430           
  Branches     1239     1239           
=======================================
  Hits         6695     6695           
  Misses        530      530           
  Partials      205      205           

Flag	Coverage Δ
unittests	90.10% <ø> (ø)

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

---

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 6c3e63e...16224b1. Read the comment docs.