bpo-40055: test_distutils leaves warnings filters unchanged (GH-20095)

distutils.tests now saves/restores warnings filters to leave them
unchanged. Importing tests imports docutils which imports
pkg_resources which adds a warnings filter.
(cherry picked from commit 6e57237faf0da8904e0130a11350cae3c5062b82)

Co-authored-by: Victor Stinner <vstinner@python.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/Lib/distutils/tests/__init__.py b/Lib/distutils/tests/__init__.py
index 1b939cb..5d2e69e 100644
--- a/Lib/distutils/tests/__init__.py
+++ b/Lib/distutils/tests/__init__.py
@@ -15,6 +15,7 @@ by import rather than matching pre-defined names.
 import os
 import sys
 import unittest
+import warnings
 from test.support import run_unittest
 
 
@@ -22,6 +23,7 @@ here = os.path.dirname(__file__) or os.curdir
 
 
 def test_suite():
+    old_filters = warnings.filters[:]
     suite = unittest.TestSuite()
     for fn in os.listdir(here):
         if fn.startswith("test") and fn.endswith(".py"):
@@ -29,6 +31,10 @@ def test_suite():
             __import__(modname)
             module = sys.modules[modname]
             suite.addTest(module.test_suite())
+    # bpo-40055: Save/restore warnings filters to leave them unchanged.
+    # Importing tests imports docutils which imports pkg_resources which adds a
+    # warnings filter.
+    warnings.filters[:] = old_filters
     return suite