Ajuda com kivy (erro: AttributeError: ‘weakref’ object has no attribute ‘cline_in_traceback’)

Estou aprendendo o kivy (então sou bem virgem no assunto gui) e me deparei com esse erro:

parte importante: AttributeError: ‘weakref’ object has no attribute ‘cline_in_traceback’

execução completa:

[INFO   ] [Logger      ] Record log in /home/albuquerque/.kivy/logs/kivy_19-04-21_53.txt [INFO   ] [Kivy        ] v1.11.0.dev0, git-eec3a30, 20190421 [INFO   ] [Python      ] v3.6.7 (default, Oct 22 2018, 11:32:17)  [GCC 8.2.0] [INFO   ] [Factory     ] 184 symbols loaded [INFO   ] [Image       ] Providers: img_tex, img_dds, img_sdl2, img_pil, img_gif (img_ffpyplayer ignored) [INFO   ] [Text        ] Provider: sdl2 [INFO   ] [Window      ] Provider: sdl2(['window_egl_rpi'] ignored) [INFO   ] [GL          ] Using the "OpenGL" graphics system [INFO   ] [GL          ] Backend used <sdl2> [INFO   ] [GL          ] OpenGL version <b'4.6.0 NVIDIA 390.116'> [INFO   ] [GL          ] OpenGL vendor <b'NVIDIA Corporation'> [INFO   ] [GL          ] OpenGL renderer <b'GeForce GT 730M/PCIe/SSE2'> [INFO   ] [GL          ] OpenGL parsed version: 4, 6 [INFO   ] [GL          ] Shading version <b'4.60 NVIDIA'> [INFO   ] [GL          ] Texture max size <16384> [INFO   ] [GL          ] Texture max units <32> [INFO   ] [Window      ] auto add sdl2 input provider [INFO   ] [Window      ] virtual keyboard not allowed, single mode, not docked  Traceback (most recent call last):    File "kivy/properties.pyx", line 840, in kivy.properties.ObservableDict.__getattr__  KeyError: 'box'   During handling of the above exception, another exception occurred:   Traceback (most recent call last):    File "main.py", line 19, in <module>      Test().run()#O método run() inicializa o app    File "/home/albuquerque/.local/lib/python3.6/site-packages/kivy/app.py", line 829, in run      root = self.build()    File "main.py", line 16, in build      return Tarefas(["a","b", "c"])    File "main.py", line 10, in __init__      self.ids.box.add_widget(Label(text=tarefa, font_size=30))#procura nos ids da classe no arquivo text.kv o id box    File "kivy/properties.pyx", line 843, in kivy.properties.ObservableDict.__getattr__  AttributeError: 'super' object has no attribute '__getattr__' Exception ignored in: functools.partial(<function _widget_destructor at 0x7f5c199612f0>, 3) Traceback (most recent call last):   File "/home/albuquerque/.local/lib/python3.6/site-packages/kivy/uix/widget.py", line 265, in _widget_destructor   File "/home/albuquerque/.local/lib/python3.6/site-packages/kivy/lang/builder.py", line 760, in unbind_widget   File "kivy/weakproxy.pyx", line 32, in kivy.weakproxy.WeakProxy.__getat 

a tela da interface não chega nem a abrir

a baixo estão os códigos:

main.py

from kivy.app import * #importar os métodos de APPP do kivy from kivy.uix.boxlayout import BoxLayout #empilha os widgets como se fossem caixas from kivy.uix.label import Label from kivy.uix.scrollview import ScrollView  class Tarefas(ScrollView):     def __init__(self, tarefas, **kwargs): #keyword arguments, o incrivel é que ele executa os argumentos colocados a mais         super().__init__(**kwargs)#chama as funções da classe BoxLayout         for tarefa in tarefas:             self.ids.box.add_widget(Label(text=tarefa, font_size=30))#procura nos ids da classe no arquivo text.kv o id box   class Test(App):#primeiro arquivo que o kivy procura (no caso, Text.kv)      def build(self): #Métod o que constroi o aplicativo         return Tarefas(["a","b", "c"])   Test().run()#O método run() inicializa o app 

test.kv

<Tarefas>:     BoxLayout:         id:box #identificação do widget         orientation:"vertical"         size_hint_y:None         height:self.minimum_height 

estou meio que desesperado, então se conseguirem me ajudar, fico desesperadamente agradecido :D: