Python Debugging: UnboundLocalError and RuntimeError

Traceback (most recent call last):
File "main.py", line 26, in main
File "launcher\ui\main_window.py", line 45, in __init__
File "launcher\ui\main_window.py", line 117, in _create_content_area
File "launcher\ui\pages\modpack_page.py", line 15, in __init__
File "launcher\ui\pages\modpack_page.py", line 76, in _create_widgets
UnboundLocalError: cannot access local variable 'btn' where it is not associated with a value
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "main.py", line 43, in <module>
File "main.py", line 38, in main
RuntimeError: lost sys.stdin