Support Kaleido v1 in Plotly.py

[emilykl]

Support both the Kaleido v0 and v1 APIs in Plotly.py.

• Update fig.write_image(), fig.to_image(), pio.write_image(), and pio.to_image() to work with both Kaleido versions
• Add deprecation warnings for:
  • the engine argument to to_image() and write_image()
  • Use of Orca
  • Use of Kaleido v0
  • Setting defaults via kaleido.scope.*
• Add a new way of setting image export defaults: plotly.io.defaults.*. This can be used in place of kaleido.scope.* and supports all the same settings: default_format, default_height, default_width, default_scale, mathjax, and topojson. pio.defaults is backwards-compatible with Kaleido v0.
• Add pio.write_images() function for generating multiple images at a time
  • Required due to the new Kaleido architecture; much faster than calling write_image() in a loop
  • Add pio.get_chrome() function which wraps kaleido.get_chrome_sync(), and add a CLI entry point plotly_get_chrome for installing Chrome from the command line
• Update tests/test_optional/test_kaleido/test_kaleido.py tests to work with either Kaleido v0 or v1. They now also actually check that an image of the right format and dimensions has been generated, as opposed to using mocking to check that the right arguments are being passed to Kaleido.
• Add test for pio.write_images()
• Update CI to run all tests with Kaleido v1, and add an additional job which runs the Kaleido tests with Kaleido v0, to protect against regressions

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TODO

• Update CI to run all tests with Kaleido v1
• Add CI job to run Kaleido tests with Kaleido v0
• Finalize UX for what happens if Chrome is not found
• Finalize UX / API for EPS
• Figure out what to do about 'renderers' Kaleido test
• Add deprecation warning for engine argument to write_image / to_image
• Re-add removed Orca support but with DeprecationWarning
• Fix DeprecationWarnings not showing up
• Expose API for setting default mathjax and topojson

[gvwilson]

Left a few comments and a question, happy to read through again as soon as you want.

[gvwilson]

do we still handle EPS?

[emilykl]

@gvwilson Following up on this — Kaleido v1 does not support EPS yet. So either we drop support for EPS entirely, or document that EPS is only available with Kaleido v0 and add an informative error message.

[gvwilson]

please do the latter - thanks

[gvwilson]

do we print a deprecation warning if this argument is used?

[emilykl]

Not yet, assuming we are in agreement about removing this argument, I'll add one

[marthacryan]

I'm in agreement that we should remove this argument

[gvwilson]

why?

[emilykl]

Part of the TODO is for me to educate myself on how Plotly currently determines PDF size when writing to PDF. :)

But the size argument is measured in pixels (at least for raster file types) and PDFs have no concept of pixels so I wouldn't expect the PDF to report the same "size" as passed in the argument necessarily.

[ayjayt]

I will also take a looksy on that issue, lets say for this and the above tomorrow. I am flying today.

[emilykl]

cc @ayjayt

[marthacryan]

Do we need to maintain backwards compatibility with older Kaleido versions here?

[marthacryan]

Are there percy tests that use kaleido to make sure that the actual images generated are correct?

[emilykl]

Quick comment to note that commit 54985b8 on this branch has been released as beta version v6.1.0b0.