[Python] Display error stream when interrupting the program

[Lucas-C]

Hi,

I am currently facing a case of Kaleido hanging forever, from Python code calling plotly.graph_objects.Figure.to_image(format="png", engine="kaleido").
I hope that this PR may be the solution I need: #149

In the meantime, adding those 3 lines allowed me access to the executable/bin/kaleido stderr when interrupting the whole program using CTRL+C:

Error stream:
[0308/083633.564952:ERROR:platform_shared_memory_region_posix.cc(47)] Descriptor access mode (0) differs from expected (2)
[0308/083633.565438:FATAL:platform_shared_memory_region_posix.cc(100)] Check failed: CheckPlatformHandlePermissionsCorrespondToMode(handle.get(), mode, size).
...

For this reason, it seems to me a useful an innocuous patch.

[alexcjohnson]

💃 Thanks @Lucas-C, this definitely looks useful!

I'll merge this now, but it may be some time before we can make a new release including it - we need to investigate #149 and the other open PRs related to hanging processes, and as you've discovered building Kaleido is a tricky process, as is testing it on all the platforms it compiles for.