ipykernel 5.3.3. compatibility issue with qt #529

Hi,

Taking the advised of @blink1073, I'm here reporting the issue found in ipykernel 5.3.3.

Basically, my qt (run in jupyter notebook) doesn't work any more after I upgraded ipykernel 5.3.3. In my testing, downgrading to 5.3.0 or 5.3.2 solves the problem, perhaps there's some incompatibility in this 5.3.3 version.

Here is what I got:

Test this code in jupyter notebook:

%matplotlib qt
import matplotlib.pyplot as plt
x = [1,2,3]
y = [5,4,5]
plt.plot(x,y)

Before upgrade to ipykernel==5.3.3

After:

Originally posted by @jacky4eyes in #525 (comment)

(My system is Win10 - 10.0.18363)