CMake deprecation warning

I'm getting deprecation warnings of policies CMP0053 and CMP0054, running CMake 3.12.3 on macOS.

CMake Deprecation Warning at submodules/cmakepp/cmakepp.cmake:25 (cmake_policy):
  The OLD behavior for policy CMP0053 will be removed from a future version
  of CMake.

  The cmake-policies(7) manual explains that the OLD behaviors of all
  policies are deprecated and that a policy should be set to OLD only under
  specific short-term circumstances.  Projects should be ported to the NEW
  behavior and not rely on setting a policy to OLD.
Call Stack (most recent call first):
  CMakeLists.txt:15 (include)


CMake Deprecation Warning at submodules/cmakepp/cmakepp.cmake:28 (cmake_policy):
  The OLD behavior for policy CMP0054 will be removed from a future version
  of CMake.

  The cmake-policies(7) manual explains that the OLD behaviors of all
  policies are deprecated and that a policy should be set to OLD only under
  specific short-term circumstances.  Projects should be ported to the NEW
  behavior and not rely on setting a policy to OLD.
Call Stack (most recent call first):
  CMakeLists.txt:15 (include)

Personally I didn't get any errors when setting both policies to NEW, but I'm only using the following functions from CMake++.

• semver_parse
• ans
• scope_import_map