--- a/src/iconolab/management/commands/importimages.py	Wed Aug 01 18:30:05 2018 +0200
+++ b/src/iconolab/management/commands/importimages.py	Wed Aug 01 18:36:33 2018 +0200
@@ -55,7 +55,7 @@
             print('-->' + target_item_image_dir, "directory created")
 
             print('#### Computing item image(s)')
-            image_file_name_fill = math.log10(len(image_files))+1
+            image_file_name_fill = int(math.log10(len(image_files)))+1
             for i, image in enumerate(image_files):
                 (_, ext) = os.path.splitext(image)
                 dest_image_name = "{0}_{1:0{2}d}.jpg".format(natural_key, i+1, image_file_name_fill)