twister: Add logging of stderr for BinaryHandlers

In the case where a test causes the test executor to crash, the stderr
is currently lost, making it hard to debug failures. This changes it
so that the process' stderr gets captured to 'handler_stderr.log' for
inspection.

Signed-off-by: Benjamin Gwin <bgwin@google.com>

Author: Benjamin Gwin

scripts/pylib/twister/twisterlib/handlers.py

@@ -307,8 +307,9 @@ def handle(self, harness):
             harness.run_robot_test(command, self)
             return
 
-        with subprocess.Popen(command, stdout=subprocess.PIPE,
-                              stderr=subprocess.PIPE, cwd=self.build_dir, env=env) as proc:
+        stderr_log = "{}/handler_stderr.log".format(self.instance.build_dir)
+        with open(stderr_log, "w+") as stderr_log_fp, subprocess.Popen(command, stdout=subprocess.PIPE,
+                              stderr=stderr_log_fp, cwd=self.build_dir, env=env) as proc:
             logger.debug("Spawning BinaryHandler Thread for %s" % self.name)
             t = threading.Thread(target=self._output_handler, args=(proc, harness,), daemon=True)
             t.start()
@@ -318,6 +319,9 @@ def handle(self, harness):
                 t.join()
             proc.wait()
             self.returncode = proc.returncode
+            if proc.returncode != 0:
+                self.instance.status = "error"
+                self.instance.reason = "BinaryHandler returned {}".format(proc.returncode)
             self.try_kill_process_by_pid()
 
         handler_time = time.time() - start_time

scripts/pylib/twister/twisterlib/runner.py

@@ -573,6 +573,7 @@ def log_info(self, filename, inline_logs, log_testcases=False):
     def log_info_file(self, inline_logs):
         build_dir = self.instance.build_dir
         h_log = "{}/handler.log".format(build_dir)
+        he_log = "{}/handler_stderr.log".format(build_dir)
         b_log = "{}/build.log".format(build_dir)
         v_log = "{}/valgrind.log".format(build_dir)
         d_log = "{}/device.log".format(build_dir)
@@ -584,6 +585,8 @@ def log_info_file(self, inline_logs):
             self.log_info("{}".format(pytest_log), inline_logs, log_testcases=True)
         elif os.path.exists(h_log) and os.path.getsize(h_log) > 0:
             self.log_info("{}".format(h_log), inline_logs)
+        elif os.path.exists(he_log) and os.path.getsize(he_log) > 0:
+            self.log_info("{}".format(he_log), inline_logs)
         elif os.path.exists(d_log) and os.path.getsize(d_log) > 0:
             self.log_info("{}".format(d_log), inline_logs)
         else:
@@ -757,6 +760,7 @@ def cleanup_artifacts(self, additional_keep: List[str] = []):
         allow = [
             os.path.join('zephyr', '.config'),
             'handler.log',
+            'handler_stderr.log',
             'build.log',
             'device.log',
             'recording.csv',