temporal: add missing import

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@61796 15284696-431f-4ddb-bdfa-cd5b030d7da7

lib/python/temporal/extract.py

@@ -12,6 +12,7 @@ for details.
 @author Soeren Gebbert
 """
 
+from grass.script import core
 from space_time_datasets import *
 from open_stds import *
 from multiprocessing import Process