bpo-38991: Remove test.support.strip_python_stderr() (GH-17490)

test.support: run_python_until_end(), assert_python_ok() and
assert_python_failure() functions no longer strip whitespaces from
stderr.
diff --git a/Lib/test/test_faulthandler.py b/Lib/test/test_faulthandler.py
index a4427a5..ac8cf46 100644
--- a/Lib/test/test_faulthandler.py
+++ b/Lib/test/test_faulthandler.py
@@ -71,9 +71,8 @@
         with support.SuppressCrashReport():
             process = script_helper.spawn_python('-c', code, pass_fds=pass_fds)
             with process:
-                stdout, stderr = process.communicate()
+                output, stderr = process.communicate()
                 exitcode = process.wait()
-        output = support.strip_python_stderr(stdout)
         output = output.decode('ascii', 'backslashreplace')
         if filename:
             self.assertEqual(output, '')