restore missing operation to CMakeLists.txt
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3471001..99bf31f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -46,6 +46,7 @@
                          "${CTR_DRBG_128_BIT_KEY_WARN_L3}"
                          "${WARNING_BORDER}")
 
+find_package(PythonInterp)
 find_package(Perl)
 if(PERL_FOUND)