Don't encode the filename.

We fixed this for when we sand_tarballs for local but not for when we
used django storages.  This should fix the filename when we get the file
from storages.

cms/djangoapps/contentstore/views/import_export.py

@@ -374,7 +374,7 @@ def export_status_handler(request, course_key_string):
         if isinstance(artifact.file.storage, FileSystemStorage):
             output_url = reverse_course_url('export_output_handler', course_key)
         elif isinstance(artifact.file.storage, S3BotoStorage):
-            filename = os.path.basename(artifact.file.name).encode('utf-8')
+            filename = os.path.basename(artifact.file.name)
             disposition = u'attachment; filename="{}"'.format(filename)
             output_url = artifact.file.storage.url(artifact.file.name, response_headers={
                 'response-content-disposition': disposition,