Simplify code in time stamper thread and make sure the dup-ed stderr is closed in the end.

runtests.py

@@ -2209,6 +2209,11 @@ def time_stamper_thread(interval=10):
     Print regular time stamps into the build logs to find slow tests.
     @param interval: time interval in seconds
     """
+    if not interval or interval < 0:
+        # Do nothing
+        yield
+        return
+
     try:
         _xrange = xrange
     except NameError:
@@ -2218,18 +2223,15 @@ def time_stamper_thread(interval=10):
     import datetime
     from time import sleep
 
-    if not interval or interval < 0:
-        # Do nothing
-        yield
-    else:
     interval = _xrange(interval * 4)
     now = datetime.datetime.now
     stop = False
 
     # We capture stderr in some places.
     # => make sure we write to the real (original) stderr of the test runner.
-        def write(s, stderr=os.dup(2)):
-            os.write(stderr, s if IS_PY2 else s.encode('ascii'))
+    stderr = os.dup(2)
+    def write(s):
+        os.write(stderr, s if type(s) is bytes else s.encode('ascii'))
 
     def time_stamper():
         while True:
@@ -2247,6 +2249,7 @@ def time_stamper_thread(interval=10):
     finally:
         stop = True
         thread.join()
+        os.close(stderr)
 
 
 def configure_cython(options):