Transform fails with error access denied

Problem

Transformation step in import fails with an error similar to "Access to path D:/Signifikant/Data/Import/ContentSet_XXX/ContentSetFiles/test.pdf is denied.".

The problem may occur in any type of imports which has attached files.

Solution

The problem is due to the files imported being either read only or not with the correct permissions.

To solve the problem, ensure files are not set as read only and that permissions allow the application to access the files.