From dfd635d03905f97cef63d59995c71808d074bf47 Mon Sep 17 00:00:00 2001
From: Morten Enemark Lund <melund@gmail.com>
Date: Wed, 25 Apr 2018 11:04:34 +0200
Subject: [PATCH] Fix problem building docs on Win

---
 xonsh/commands_cache.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xonsh/commands_cache.py b/xonsh/commands_cache.py
index 0bf16f6ba..1f3505939 100644
--- a/xonsh/commands_cache.py
+++ b/xonsh/commands_cache.py
@@ -61,7 +61,7 @@ class CommandsCache(cabc.Mapping):
          name on Windows as a list, conserving the ordering in `PATHEXT`.
          Returns a list as `name` being the only item in it on other platforms."""
         if ON_WINDOWS:
-            pathext = builtins.__xonsh_env__.get('PATHEXT')
+            pathext = builtins.__xonsh_env__.get('PATHEXT', [])
             name = name.upper()
             return [
                 name + ext