unittest.result.TestResult does not create its buffers until they're used. It uses StringIO not cStringIO. Issue 8333.
diff --git a/Lib/unittest/result.py b/Lib/unittest/result.py
index b9045f4..4b7cde6 100644
--- a/Lib/unittest/result.py
+++ b/Lib/unittest/result.py
@@ -4,7 +4,7 @@
import sys
import traceback
-from cStringIO import StringIO
+from StringIO import StringIO
from . import util
from functools import wraps
@@ -46,8 +46,8 @@
self.unexpectedSuccesses = []
self.shouldStop = False
self.buffer = False
- self._stdout_buffer = StringIO()
- self._stderr_buffer = StringIO()
+ self._stdout_buffer = None
+ self._stderr_buffer = None
self._original_stdout = sys.stdout
self._original_stderr = sys.stderr
self._mirrorOutput = False
@@ -60,6 +60,9 @@
self.testsRun += 1
self._mirrorOutput = False
if self.buffer:
+ if self._stderr_buffer is None:
+ self._stderr_buffer = StringIO()
+ self._stdout_buffer = StringIO()
sys.stdout = self._stdout_buffer
sys.stderr = self._stderr_buffer