[WP8] Reference rewriter error

Hello

We have a Windows Phone 8 projects that has been working fine in the last couple of months, without any issue. We been using classes from System.IO without any problem, like the classes FileInfo and DirectoryInfo.

Now we have upgraded Unity from 4.6.8 to 5.2.2, and suddenly errors were introduced. We are able to build the Unity projects and a Visual Studio solution is made as per usual, but when Unity finished building errors are shown the in console. (The build seems to complete anyways)

The errors seem to relate to FileInfo and DirectoryInfo, and when we deploy the application on a device, our app can not read and write to disk using this functionality.

We receive 3 errors, looking like this:

As mentioned earlier, we did not have any issues until updating unity version. Any input appreciated.

Kind regards,
Martin