Merge pull request #207 from pukkandan/thumbnail-rename

[ffmpeg] Fix for os.rename error when embedding thumbnail to video in a different drive on windows

diff --cc youtube_dlc/postprocessor/embedthumbnail.py
index 7ca0ce6e5fafecacbcfb31dc3e09119f066ca607,2ff3cff6910fef6649a16705362e56e72396486d..e9f2161a01e06a0c7b6ffc28c80aaa70ec69bb6e
--- 1/youtube_dlc/postprocessor/embedthumbnail.py
--- 2/youtube_dlc/postprocessor/embedthumbnail.py
+++ b/youtube_dlc/postprocessor/embedthumbnail.py
@@@ -89,13 -89,14 +89,15 @@@ class EmbedThumbnailPP(FFmpegPostProces
              os.rename(encodeFilename(temp_filename), encodeFilename(filename))
  
          elif info['ext'] == 'mkv':
-             os.rename(encodeFilename(thumbnail_filename), encodeFilename('cover.jpg'))
              old_thumbnail_filename = thumbnail_filename
-             thumbnail_filename = 'cover.jpg'
+             thumbnail_filename = os.path.join(os.path.dirname(old_thumbnail_filename), 'cover.jpg')
+             if os.path.exists(thumbnail_filename):
+                 os.remove(encodeFilename(thumbnail_filename))
+             os.rename(encodeFilename(old_thumbnail_filename), encodeFilename(thumbnail_filename))
  
              options = [
 -                '-c', 'copy', '-attach', thumbnail_filename, '-metadata:s:t', 'mimetype=image/jpeg']
 +                '-c', 'copy', '-map', '0',
 +                '-attach', thumbnail_filename, '-metadata:s:t', 'mimetype=image/jpeg']
  
              self._downloader.to_screen('[ffmpeg] Adding thumbnail to "%s"' % filename)