Issue #12400: regrtest.runtest() uses stream.seek(0) before .truncate()
.truncate(0) doesn't rewind.
diff --git a/Lib/test/regrtest.py b/Lib/test/regrtest.py
index f1ef715..14fa005 100755
--- a/Lib/test/regrtest.py
+++ b/Lib/test/regrtest.py
@@ -791,9 +791,12 @@
# tests keep a reference to sys.stdout or sys.stderr
# (eg. test_argparse).
if runtest.stringio is None:
- runtest.stringio = io.StringIO()
- stream = runtest.stringio
- stream.truncate(0)
+ stream = io.StringIO()
+ runtest.stringio = stream
+ else:
+ stream = runtest.stringio
+ stream.seek(0)
+ stream.truncate()
orig_stdout = sys.stdout
orig_stderr = sys.stderr