Update cli.py

Author: Kshemaahna

caltechdata_api/cli.py

@@ -403,7 +403,8 @@ def upload_supporting_file(record_id=None):
             files = [
                 f for f in os.listdir() if not f.endswith(".json") and os.path.isfile(f)
             ]
-            print((""+ str(++idx) + "/ \n").join(files))
+            idx+=1
+            print((""+ str(idx) + "/ \n").join(files))
             while True:
                 filename = get_user_input(
                     "Enter the filename to upload as a supporting file (or '*' to get all files currently in the directory, or the index number of the file as displayed followed by a /, otherwise 'n' to finish): "