CMake Error at .*/Modules/ExternalData.cmake:[0-9]+ \(message\):
  Bad %\(algo:\) in URL template:

   file:///path/to/%\(algo:\)/%\(hash\)

  The transform name must be a valid C identifier.
Call Stack \(most recent call first\):
  BadAlgoMap1\.cmake:[0-9]+ \(ExternalData_Add_Target\)
  CMakeLists\.txt:[0-9]+ \(include\)