SF bug 563750 (Alex Martelli): posix_tmpfile():

The file returned by tmpfile() has mode w+b, so use that in the call
to PyFile_FromFile().

Bugfix candidate.
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 9d7c3c2..95f4613 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -5194,7 +5194,7 @@
     fp = tmpfile();
     if (fp == NULL)
         return posix_error();
-    return PyFile_FromFile(fp, "<tmpfile>", "w+", fclose);
+    return PyFile_FromFile(fp, "<tmpfile>", "w+b", fclose);
 }
 #endif