gh-152132: Close stderr_copy in test_api.test_run (#153591)

Previously, the test was leaking a file descriptor.

Author: vstinner

Lib/test/test_capi/test_run.py

@@ -310,13 +310,15 @@ def check_run_interactive(self, run, encode_filename, use_loop=False):
             # supported". In this case, run the test without redirecting
             # stderr to a temporary file.
             self._check_run_interactive(run, encode_filename, use_loop)
-        else:
-            with tempfile.TemporaryFile() as tmp:
-                try:
-                    os.dup2(tmp.fileno(), STDERR_FD)
-                    self._check_run_interactive(run, encode_filename, use_loop)
-                finally:
-                    os.dup2(stderr_copy, STDERR_FD)
+            return
+
+        with tempfile.TemporaryFile() as tmp:
+            try:
+                os.dup2(tmp.fileno(), STDERR_FD)
+                self._check_run_interactive(run, encode_filename, use_loop)
+            finally:
+                os.dup2(stderr_copy, STDERR_FD)
+                os.close(stderr_copy)
 
     def test_run_interactiveone(self):
         # Test PyRun_InteractiveOne()