Make sure only compatible python versions get used.

Fixes #196

bindings/python/CMakeLists.txt

@@ -2,6 +2,8 @@ if(NOT BUILD_SHARED_LIBS)
   message(ERROR "Python bindings are only supported for shared libraries")
 endif()
 
+set(Python_ADDITIONAL_VERSIONS 3 2.7)
+find_package(PythonInterp REQUIRED)
 find_package(PythonLibsNew REQUIRED)
 
 pybind11_add_module(adios2py MODULE

cmake/DetectOptions.cmake

@@ -95,6 +95,8 @@ list(INSERT CMAKE_MODULE_PATH 0
 )
 if(ADIOS2_USE_Python STREQUAL AUTO)
   if(BUILD_SHARED_LIBS)
+    set(Python_ADDITIONAL_VERSIONS 3 2.7)
+    find_package(PythonInterp)
     find_package(PythonLibsNew)
     if(PYTHONLIBS_FOUND)
       if(ADIOS2_HAVE_MPI)