Example on Python 3.6:

haypo@selma$ ./python -m test test_warnings  test_warnings 
Run tests sequentially
0:00:00 load avg: 1.74 [1/2] test_warnings
0:00:01 load avg: 1.68 [2/2] test_warnings
/home/haypo/prog/python/3.6/Lib/test/test_warnings/__init__.py:902: UserWarning: foo
  wmod.warn("foo")
/home/haypo/prog/python/3.6/Lib/test/test_warnings/__init__.py:1000: UserWarning: foo
  wmod.warn("foo")
/home/haypo/prog/python/3.6/Lib/test/test_warnings/__init__.py:964: UserWarning: This is a warning
  wmod.warn(text)
/home/haypo/prog/python/3.6/Lib/test/test_warnings/__init__.py:986: UserWarning: This is a warning
  wmod.warn(text)
/home/haypo/prog/python/3.6/Lib/test/test_warnings/__init__.py:148: UserWarning: FilterTests.test_always
  self.module.warn(message, UserWarning)
/home/haypo/prog/python/3.6/Lib/test/test_warnings/__init__.py:159: UserWarning: FilterTests.test_always_after_ignore
  self.module.warn(message, UserWarning)
/home/haypo/prog/python/3.6/Lib/test/test_warnings/__init__.py:180: UserWarning: FilterTests.test_default
  self.module.warn(message, UserWarning)
/home/haypo/prog/python/3.6/Lib/test/test_warnings/__init__.py:249: UserWarning: handle normally
  self.module.warn(text)
/home/haypo/prog/python/3.6/Lib/test/test_warnings/__init__.py:135: UserWarning: FilterTests.test_ignore_after_default
  self.module.warn(message, UserWarning)
/home/haypo/prog/python/3.6/Lib/test/test_warnings/__init__.py:195: UserWarning: FilterTests.test_module
  self.module.warn(message, UserWarning)
f.py:42: UserWarning: b
__init__.py:42: UserWarning: FilterTests.test_once
/home/haypo/prog/python/3.6/Lib/test/test_warnings/data/stacklevel.py:9: UserWarning: spam1
  warnings.warn(message, stacklevel=stacklevel)
/home/haypo/prog/python/3.6/Lib/test/test_warnings/__init__.py:354: UserWarning: multi 0
  self.module.warn(text)
/home/haypo/prog/python/3.6/Lib/test/__main__.py:9: UserWarning: spam9
__main__:9: UserWarning: spam11
__main__:9: UserWarning: spam10
test.test_warnings.data.stacklevel:9: UserWarning: spam8
/home/haypo/prog/python/3.6/Lib/test/test_warnings/data/stacklevel.py:9: UserWarning: spam3
  warnings.warn(message, stacklevel=stacklevel)
/home/haypo/prog/python/3.6/Lib/test/test_warnings/__init__.py:415: DeprecationWarning: module-level warning
  import test.test_warnings.data.import_warning
nonasciié€:1: UserWarning: text
/home/haypo/prog/python/3.6/Lib/test/test_warnings/__init__.py:365: UserWarning: <class 'Warning'>
  self.module.warn(ob)
/home/haypo/prog/python/3.6/Lib/test/test_warnings/__init__.py:561: MyWarningClass: good warning category
  self.module.warn('good warning category', MyWarningClass)
<test>:42: UserWarning: defaultaction test
test.test_warnings:778: UserWarning: test
file:42: UserWarning: onceregistry test
/home/haypo/prog/python/3.6/Lib/test/test_warnings/__init__.py:741: UserWarning: Warning!
  self.module.warn('Warning!')
/home/haypo/prog/python/3.6/Lib/unittest/case.py:178: UserWarning: Warning!
  callable_obj(*args, **kwargs)
test test_warnings failed -- multiple errors occurred; run in verbose mode for details
test_warnings failed
1 test OK.

1 test failed:
    test_warnings

Total duration: 3 sec
Tests result: FAILURE