Remove workaround for older Pythons

importlib.import_module is available since Python 2.7.

import_export/formats/base_formats.py

@@ -4,6 +4,7 @@ from django.utils.six import moves
 import sys
 import warnings
 import tablib
+from importlib import import_module
 
 try:
     from tablib.compat import xlrd
@@ -35,12 +36,6 @@ except ImportError:
         XLSX_IMPORT = False
 
 
-try:
-    from importlib import import_module
-except ImportError:
-    from django.utils.importlib import import_module
-
-
 class Format(object):
     def get_title(self):
         return type(self)