Use of com.google.appengine.repackaged may result in your app breaking without warning.

I got this nasty error on the repackaged version of Base64 after upgrading to app-engine 1.6.1 on a project:

Use of com.google.appengine.repackaged may result in your app breaking without warning.

You can make it go away by switching to org.apache.commons.codec.binary.Base64, that can be found on the commons-codec library. Mapping of the encode/decode methods is pretty straightforward:

• encode --> encodeBase64String
• decode --> decodeBase64

Or something like that.