Update stdout and stderr in manual error creation to be bytes

Author: cmaloney

Lib/test/support/strace_helper.py

@@ -83,8 +83,8 @@ def _make_error(reason, details):
             strace_returncode=-1,
             python_returncode=-1,
             event_bytes=f"error({reason},details={details}) = -1".encode('utf-8'),
-            stdout=res.out if res else "",
-            stderr=res.err if res else "")
+            stdout=res.out if res else b"",
+            stderr=res.err if res else b"")
 
     # Run strace, and get out the raw text
     try: