MeshLinePlot prevents unit tests from running

Describe the bug Instantiating a MeshLinePlot anywhere in a unit testing script prevents pytest and unittest from discovering and running tests.

To Reproduce Uncomment either MeshLinePlot() call in the below script.

# test_container.py
import unittest
from kivy_garden.graph import MeshLinePlot

#mesh = MeshLinePlot()

class Container():
    def __init__(self, id):
        self.id = id
        #self.mesh = MeshLinePlot()

class TestOne(unittest.TestCase):
    def test_dummy(self):
        print('In dummy_test()')
        self.assertEqual(1, 1)

    def test_class_init(self):
        print('In test_class_init()')
        c = Container(1)
        self.assertEqual(c.id, 1)

if __name__ == '__main__':
    unittest.main()

Expected behavior Unit tests are discovered and run as expected with pytest and/or unittest.

Logs/output Result when uncommenting the instantiation in Container:

> python test_container.py
[INFO   ] [Logger      ] Record log in C:\Users\ganzk\.kivy\logs\kivy_20-07-28_13.txt
[INFO   ] [deps        ] Successfully imported "kivy_deps.glew" 0.2.0
[INFO   ] [deps        ] Successfully imported "kivy_deps.sdl2" 0.2.0
[INFO   ] [Kivy        ] v1.11.1
[INFO   ] [Kivy        ] Installed at "c:\Users\ganzk\Desktop\peaks\kivy_env\lib\site-packages\kivy\__init__.py"
[INFO   ] [Python      ] v3.7.3 (v3.7.3:ef4ec6ed12, Mar 25 2019, 22:22:05) [MSC v.1916 64 bit (AMD64)]
[INFO   ] [Python      ] Interpreter at "c:\Users\ganzk\Desktop\peaks\kivy_env\Scripts\python.exe"
[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
In test_class_init()

Using pytest instead:

=== test session starts ===
> pytest test_container.py
platform win32 -- Python 3.7.3, pytest-5.4.3, py-1.9.0, pluggy-0.13.1
rootdir: C:\Users\ganzk\Desktop\peaks
collected 0 items                                                                                                                                      
== no tests ran in 0.00s ==

Platform (please complete the following information):

Windows 10
Python 3.7.3, kivy-garden.graph 0.4.0, kivy 1.11.1

kivy-garden / graph

MeshLinePlot prevents unit tests from running #30