[pitivi] medialibrary: Fix XDG_CACHE_HOME usage

[Alexandru Băluț <alexbalut src gnome org>]

commit 0ef993a0408d542709b51c15be58d911c8fb988d
Author: Alexandru Băluț <alexandru balut gmail com>
Date:   Wed Oct 5 16:19:04 2016 +0200

    medialibrary: Fix XDG_CACHE_HOME usage
    
    Differential Revision: https://phabricator.freedesktop.org/D1354

 pitivi/medialibrary.py |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/pitivi/medialibrary.py b/pitivi/medialibrary.py
index 42a38b4..67d7638 100644
--- a/pitivi/medialibrary.py
+++ b/pitivi/medialibrary.py
@@ -729,7 +729,7 @@ class MediaLibraryWidget(Gtk.Box, Loggable):
             quoted_uri = quote_uri(real_uri)
             thumbnail_hash = md5(quoted_uri.encode()).hexdigest()
             try:
-                thumb_dir = os.environ['XDG_CACHE_HOME']
+                thumb_dir = os.path.join(os.environ["XDG_CACHE_HOME"], "thumbnail")
                 thumb_64, thumb_128 = self._getThumbnailInDir(
                     thumb_dir, thumbnail_hash)
             except KeyError: