remove python 2 support

Author: sy-c

CMakeLists.txt

@@ -78,11 +78,6 @@ if(NOT APPLE)
   find_package(Python3 3.6 COMPONENTS Interpreter Development)
   if(Python3_FOUND)
     set(boost_python_component "python${Python3_VERSION_MAJOR}${Python3_VERSION_MINOR}")
-  else()
-    # Backwards compatible. Can be removed once the Python3 recipe is stable
-    message(WARNING "Python 3 was not found: falling back to Python 2")
-    find_package(Python2 2.7 COMPONENTS Development REQUIRED)
-    set(boost_python_component "python27")
   endif()
 endif()