I had the same Problem with our Pydio Cloud on Ubuntu 14.04.
To make the upload work I made a backup of the UploadedFile.php and removed the array that contains the error messages.
There are only two calls for that Array inside the php so I removed the two calls, the error message is now a static output.
Now the upload is working again.
If there will be a fix for that bug I can restore the original file again.
