Ensure image files & Record can be cleaned when a user is removed

app.py

@@ -162,6 +162,13 @@ def FUN_delete_user(id):
     if session.get("current_user", None) == "ADMIN":
         if id == "ADMIN": # ADMIN account can't be deleted.
             return abort(403)
+
+        # [1] Delete this user's images in image pool
+        images_to_remove = [x[0] for x in list_images_for_user(id)]
+        for f in images_to_remove:
+            image_to_delete_from_pool = [y for y in [x for x in os.listdir(app.config['UPLOAD_FOLDER'])] if y.split("-", 1)[0] == f][0]
+            os.remove(os.path.join(app.config['UPLOAD_FOLDER'], image_to_delete_from_pool))
+        # [2] Delele the records in database files
         delete_user_from_db(id)
         return(redirect(url_for("FUN_admin")))
     else:

database.py

@@ -42,7 +42,9 @@ def delete_user_from_db(id):
     _conn.commit()
     _conn.close()
 
-    # when we delete a user from database USERS, we also need to delete all his or her images data from database IMAGES
+    # when we delete a user from database USERS, we also need to 
+    # [1] delete all his or her images from image pool (done in app.py)
+    # [2] delete all his or her images records from database IMAGES
     _conn = sqlite3.connect(image_db_file_location)
     _c = _conn.cursor()
     _c.execute("delete from images where owner = '" + id + "';")