Issue #8533: Write tracebacks and failed tests to sys.stderr instead of

sys.stdout to avoid UnicodeEncodeError (use backslashreplace error handler)

Lib/test/regrtest.py

@@ -939,8 +939,8 @@ def runtest_inner(test, verbose, quiet,
         print("test", test, "crashed --", str(type) + ":", value)
         sys.stdout.flush()
         if verbose or debug:
-            traceback.print_exc(file=sys.stdout)
+            traceback.print_exc(file=sys.stderr)
-            sys.stdout.flush()
+            sys.stderr.flush()
         return FAILED, test_time
     else:
         if refleak:

Lib/test/support.py

@@ -1020,7 +1020,7 @@ def check_impl_detail(**guards):
 def _run_suite(suite):
     """Run tests from a unittest.TestSuite-derived class."""
     if verbose:
-        runner = unittest.TextTestRunner(sys.stdout, verbosity=2)
+        runner = unittest.TextTestRunner(sys.stderr, verbosity=2)
     else:
         runner = BasicTestRunner()
 

Misc/NEWS

@@ -1198,6 +1198,9 @@ Documentation
 Tests
 -----
 
+- Issue #8533: Write tracebacks and failed tests to sys.stderr instead of
+  sys.stdout to avoid UnicodeEncodeError (use backslashreplace error handler)
+
 - Issue #8576: Remove use of find_unused_port() in test_smtplib and
   test_multiprocessing.  Patch by Paul Moore.