Cache keys should be unicode.

openassessment/fileupload/backends/filesystem.py

@@ -5,6 +5,7 @@ from .. import exceptions
 from django.conf import settings
 import django.core.cache
 from django.core.urlresolvers import reverse
+from django.utils.encoding import smart_text
 
 
 class Backend(BaseBackend):
@@ -71,8 +72,8 @@ def make_upload_url_available(url_key_name, timeout):
         url_key_name (str): key that uniquely identifies the upload url
         timeout (int): time in seconds before the url expires
     """
-    return get_cache().set(
-        get_upload_cache_key(url_key_name),
+    get_cache().set(
+        smart_text(get_upload_cache_key(url_key_name)),
         1, timeout
     )
 
@@ -84,8 +85,8 @@ def make_download_url_available(url_key_name, timeout):
         url_key_name (str): key that uniquely identifies the url
         timeout (int): time in seconds before the url expires
     """
-    return get_cache().set(
-        get_download_cache_key(url_key_name),
+    get_cache().set(
+        smart_text(get_download_cache_key(url_key_name)),
         1, timeout
     )
 
@@ -93,13 +94,13 @@ def is_upload_url_available(url_key_name):
     """
     Return True if the corresponding upload URL is available.
     """
-    return get_cache().get(get_upload_cache_key(url_key_name)) is not None
+    return get_cache().get(smart_text(get_upload_cache_key(url_key_name))) is not None
 
 def is_download_url_available(url_key_name):
     """
     Return True if the corresponding download URL is available.
     """
-    return get_cache().get(get_download_cache_key(url_key_name)) is not None
+    return get_cache().get(smart_text(get_download_cache_key(url_key_name))) is not None
 
 def get_upload_cache_key(url_key_name):
     return "upload/" + url_key_name

openassessment/fileupload/views_filesystem.py

@@ -17,6 +17,8 @@ def filesystem_storage(request, key):
     """
     Uploading and download files to the local filesystem backend.
     """
+    if isinstance(key, unicode):
+        key = key.encode("utf-8")
     if request.method == "PUT":
         if not is_upload_url_available(key):
             raise Http404()