Tkinter asyncio matplotlib crash: long-running async tasks using matplotlib and launched by a tkinter GUI

tksyncplot.py

import asyncio
import matplotlib
matplotlib.use('TkAgg')
import tkinter as tk
from tkinter import ttk
from skimage._shared._tempfile import temporary_file
import numpy as np


@asyncio.coroutine
def _async(func, *args):
    loop = asyncio.get_event_loop()
    return (yield from loop.run_in_executor(None, func, *args))


STANDARD_MARGIN = (3, 3, 12, 12)


def long_computation():
    import time
    time.sleep(4)
    import matplotlib.pyplot as plt
    fig, ax = plt.subplots()
    ax.imshow(np.random.rand(500, 500))
    with temporary_file(suffix='.png') as fname:
        fig.savefig(fname)


class MainWindow(tk.Tk):
    def __init__(self):
        super().__init__()
        self.title('I gonna die')
        main = ttk.Frame(master=self, padding=STANDARD_MARGIN)
        main.grid(row=0, column=0, sticky='nsew')
        fsync = long_computation
        fasync = lambda: asyncio.ensure_future(_async(long_computation))
        # swap in command=fsync instead of fasync below for working slow app
        button = ttk.Button(master=main, padding=STANDARD_MARGIN,
                            text='Run stuff',
                            command=fasync)
        button.grid(row=0, column=0)
        main.pack()


def tk_update(loop, app):
    try:
        app.update()
    except tk.TclError as e:
        loop.stop()
        return
    loop.call_later(.01, tk_update, loop, app)


def main():
    loop = asyncio.get_event_loop()
    app = MainWindow()
    #app.mainloop()
    tk_update(loop, app)
    loop.run_forever()


if __name__ == '__main__':
    main()