Corrected bug in list2cmdline wrt backslashes. Fixes #1083306.
diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index 61effde..e72e260 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -532,6 +532,7 @@
             result.extend(bs_buf)
 
         if needquote:
+            result.extend(bs_buf)
             result.append('"')
 
     return ''.join(result)