Security patch for Unix by Chris McDonough.

This uses the same precautions when trying to find a temporary
directory as when the actual tempfile is created (using O_CREAT and
O_EXCL).  On non-posix platforms, nothing is changed.

Lib/tempfile.py

@@ -43,6 +43,20 @@ def gettempdir():
     for dir in attempdirs:
         try:
            filename = os.path.join(dir, testfile)
+           if os.name == 'posix':
+               try:
+                   fd = os.open(filename, os.O_RDWR|os.O_CREAT|os.O_EXCL, 0700)
+               except OSError:
+                   pass
+               else:
+                   fp = os.fdopen(fd, 'w')
+                   fp.write('blat')
+                   fp.close()
+                   os.unlink(filename)
+                   del fp, fd
+                   tempdir = dir
+                   break
+           else:
                fp = open(filename, 'w')
                fp.write('blat')
                fp.close()