make find_package for Python3 more specific

test/CMakeLists.txt

@@ -2,13 +2,15 @@
 # Distributed under the Boost Software License, Version 1.0.
 # See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt
 
-find_package(Python3)
+find_package(Python3 COMPONENTS Interpreter)
 if (Python3_FOUND)
   # checks that b2 and cmake are in sync
   add_test(NAME runpy-${PROJECT_NAME}_check_build_system COMMAND ${Python3_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/check_build_system.py)
 
   # checks that all headers are included in odr test
   add_test(NAME runpy-${PROJECT_NAME}_check_odr_test COMMAND ${Python3_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/check_odr_test.py)
+else()
+MESSAGE(WARNING "Python interpreter not found, cannot check for odr violations and build system consistency")
 endif()
 
 include(BoostTest OPTIONAL RESULT_VARIABLE HAVE_BOOST_TEST)