Improve Python version finding mechanism

CMakeLists.txt

-cmake_minimum_required(VERSION 3.8)
+cmake_minimum_required(VERSION 3.12)
 
 project(AOFlagger)
 
@@ -49,6 +49,15 @@ if(GIT_FOUND AND EXISTS "${PROJECT_SOURCE_DIR}/.git")
   endif()
 endif()
 
+# Python needs to be found before pybind11 to avoid finding different versions
+# of python
+find_package(
+  Python
+  COMPONENTS Interpreter Development
+  REQUIRED)
+message(STATUS "Using python version ${Python_VERSION}")
+include_directories(SYSTEM ${Python_INCLUDE_DIRS})
+
 list(APPEND ExternalSubmoduleDirectories aocommon pybind11)
 foreach(ExternalSubmodule IN LISTS ExternalSubmoduleDirectories)
   if(NOT EXISTS ${CMAKE_SOURCE_DIR}/external/${ExternalSubmodule})
@@ -96,10 +105,6 @@ endif(GSL_INCLUDE_DIR)
 find_package(Threads REQUIRED)
 
 find_package(PNG REQUIRED)
-find_package(PythonLibs 3 REQUIRED)
-find_package(PythonInterp REQUIRED)
-message(STATUS "Using python version ${PYTHON_VERSION_STRING}")
-include_directories(SYSTEM ${PYTHON_INCLUDE_DIRS})
 
 # boost::alignment requires Boost 1.56
 find_package(Boost 1.56.0 REQUIRED COMPONENTS date_time filesystem system
@@ -333,7 +338,7 @@ set(ALL_LIBRARIES
     ${CASACORE_LIBRARIES}
     ${FFTW3_LIB}
     ${CFITSIO_LIBRARY}
-    ${PYTHON_LIBRARIES}
+    ${Python_LIBRARIES}
     ${PNG_LIBRARIES}
     ${LUA_LIBRARIES}
     ${Boost_LIBRARIES}