[Kivy] Program ending unexpectedly without output

[test]

Hello!
I just started learning to use kivy. I copied an example from the docs into nano, but it doesn't show any output and terminates on its own.

Here is the code:

import kivy
kivy.require ('1.10.1')

from kivy.app import App
from kivy.uix.label import Label
from kivy.uix.gridlayout import GridLayout
from kivy.uix.textinput import TextInput

class Login(GridLayout):
	def __init__(self, **kwargs):
		super(Login, self).__init__(**kwargs)
		self.cols = 2
		self.add_widget(Label(text='Username'))
		self.username = TextInput(multiline=False)
		self.add_widget(self.username)
		self.add_widget(Label(text='Password'))
		self.password = TextInput(multiline=False, password=True)
		self.add_widget(self.password)


class MyApp(App):
	def build(self):
		return Login()
#        return Label(text='Hello world!')

if __name__ == '__main__':
	MyApp().run()

the output in the console is the following:

Output:
[INFO   ] [Logger      ] Record log in /home/comp/.kivy/logs/kivy_18-11-09_6.txt
[INFO   ] [Kivy        ] v1.10.1
[INFO   ] [Python      ] v3.6.5 (default, Apr  1 2018, 05:46:30) 
[GCC 7.3.0]
[INFO   ] [Factory     ] 194 symbols loaded
[INFO   ] [Image       ] Providers: img_tex, img_dds, img_sdl2, img_pil, img_gif (img_ffpyplayer ignored)
[INFO   ] [Text        ] Provider: pil(['text_sdl2'] ignored)

where am i making the mistake??