a.rb

$ rwt -q pytest pytest-warnings -- -m pytest -rw test-warnings.py
====================================== test session starts =======================================
platform darwin -- Python 3.6.1, pytest-3.0.7, py-1.4.33, pluggy-0.4.0
rootdir: /Users/jaraco, inifile:
plugins: warnings-0.2.0
collected 1 items 

test-warnings.py .

===================================== pytest-warning summary =====================================
WW0 in test-warnings.py:2 the following warning was recorded:
 test-warnings.py:4: DeprecationWarning: deprecated
  warnings.warn("deprecated", DeprecationWarning)

========================== 1 passed, 1 pytest-warnings in 0.01 seconds ===========================