Python2 is dumb.

.travis.yml

@@ -4,6 +4,7 @@ python:
 #  - "3.2" # 3.2 is broken, for some reason
   - "3.3"
   - "3.4"
+  - "3.5"
 # command to install dependencies, e.g. pip install -r requirements.txt --use-mirrors
 install: pip install -r requirements.txt --use-mirrors
 # command to run tests, e.g. python setup.py test

flask_s3.py

@@ -130,7 +130,14 @@ def _static_folder_path(static_url, static_folder, static_asset):
                          (static_asset, static_folder))
     rel_asset = static_asset[len(static_folder):]
     # Now bolt the static url path and the relative asset location together
-    return six.u('%s/%s' % (static_url.rstrip('/'), rel_asset.lstrip('/')))
+    if six.PY2:
+        if not isinstance(static_url, unicode) or not isinstance(rel_asset, unicode):
+            u = six.u
+        else:
+            u = str
+    else:
+        u = str
+    return u('%s/%s' % (static_url.rstrip('/'), rel_asset.lstrip('/')))
 
 
 def _write_files(s3, app, static_url_loc, static_folder, files, bucket,