CMake Error at .*/Modules/ExternalData.cmake:[0-9]+ \(message\):
  Data file referenced by argument

    DATA{../NotUnderRoot.txt}

  does not lie under the top-level source directory

    .*/Tests/RunCMake/ExternalData

Call Stack \(most recent call first\):
  .*
  NotUnderRoot.cmake:2 \(ExternalData_Add_Test\)