'NoneType' object has no attribute 'username'

This error message typically occurs when you try to access an attribute or method of an object that is of type 'NoneType'. In other words, the object you are trying to access does not exist or has not been properly initialized.

In this specific case, it seems that you are trying to access the 'username' attribute of an object that is of type 'NoneType'. This could happen, for example, if you are trying to access a user object that has not been properly authenticated or is not available in the current context.

To fix this error, you need to make sure that the object you are trying to access actually exists and has been properly initialized. You may also want to add some error handling code to your program to catch this type of error and handle it appropriately.