Stackless issue #167: replace printf() by PySys_WriteStderr()

printf() was used to emit parts of an error message, if there is a
pending error while entering Stackless subsystem.
(cherry picked from commit 8a44a5f)

Author: Anselm Kruis

Stackless/changelog.txt

@@ -9,6 +9,11 @@ What's New in Stackless 3.X.X?
 
 *Release date: 20XX-XX-XX*
 
+- https://github.com/stackless-dev/stackless/issues/167
+  Replace 'printf(...)' calls by PySys_WriteStderr(...). They are used to emit
+  an error message, if there is a pending error while entering Stackless
+  subsystem.
+
 - https://github.com/stackless-dev/stackless/issues/154
   Fix a minor bug in STACKLESS_PROMOTE_WRAPPER and STACKLESS_PROMOTE_METHOD.
 

Stackless/module/scheduling.c

@@ -1262,9 +1262,9 @@ slp_initialize_main_and_current(void)
         Py_XINCREF(value);
         Py_XINCREF(traceback);
         PyErr_Restore(type, value, traceback);
-        printf("Pending error while entering Stackless subsystem:\n");
+        PySys_WriteStderr("Pending error while entering Stackless subsystem:\n");
         PyErr_Print();
-        printf("Above exception is re-raised to the caller.\n");
+        PySys_WriteStderr("Above exception is re-raised to the caller.\n");
         PyErr_Restore(type, value, traceback);
 #endif
     return 1;