Improve CMake Python code

* We have code with u'' which means minimum version is 3.3
* Python 3.8 is already in development, be a bit more future proof

CMakeLists.txt

@@ -687,8 +687,8 @@ if( KICAD_SCRIPTING OR KICAD_SCRIPTING_MODULES )
     include( ${SWIG_USE_FILE} )
 
     if( KICAD_SCRIPTING_PYTHON3 )
-        set( PythonInterp_FIND_VERSION 3 )
-        set( PythonLibs_FIND_VERSION 3 )
+        set( PythonInterp_FIND_VERSION 3.3 )
+        set( PythonLibs_FIND_VERSION 3.3 )
     else()
         # force a python version < 3.0
         set( PythonInterp_FIND_VERSION 2.6 )
@@ -732,7 +732,7 @@ if( KICAD_SCRIPTING OR KICAD_SCRIPTING_MODULES )
     message( STATUS "Python module install path: ${PYTHON_DEST}" )
 
     if( KICAD_SCRIPTING_PYTHON3 )
-        find_package( PythonLibs 3 REQUIRED )
+        find_package( PythonLibs 3.3 REQUIRED )
     else()
         find_package( PythonLibs 2.6 REQUIRED )
     endif()

CMakeModules/FindPythonInterp.cmake

@@ -37,7 +37,7 @@ unset(_Python_NAMES)
 
 set(_PYTHON1_VERSIONS 1.6 1.5)
 set(_PYTHON2_VERSIONS 2.7 2.6 2.5 2.4 2.3 2.2 2.1 2.0)
-set(_PYTHON3_VERSIONS 3.3 3.2 3.1 3.0)
+set(_PYTHON3_VERSIONS 3.8 3.7 3.6 3.5 3.4 3.3 3.2 3.1 3.0)
 
 if(PythonInterp_FIND_VERSION)
     if(PythonInterp_FIND_VERSION MATCHES "^[0-9]+\\.[0-9]+(\\.[0-9]+.*)?$")

CMakeModules/FindPythonLibs.cmake

@@ -44,7 +44,7 @@ cmake_find_frameworks(Python)
 
 set(_PYTHON1_VERSIONS 1.6 1.5)
 set(_PYTHON2_VERSIONS 2.7 2.6 2.5 2.4 2.3 2.2 2.1 2.0)
-set(_PYTHON3_VERSIONS 3.7 3.6 3.5 3.4 3.3 3.2 3.1 3.0)
+set(_PYTHON3_VERSIONS 3.8 3.7 3.6 3.5 3.4 3.3 3.2 3.1 3.0)
 
 if(PythonLibs_FIND_VERSION)
     if(PythonLibs_FIND_VERSION MATCHES "^[0-9]+\\.[0-9]+(\\.[0-9]+.*)?$")