runJavaScript() calls failing on unexpected keyword argument 'asynchronous'

[dhomeier]

Describe the bug
TestWWTDataViewer.test_save_tour() fails on

>       self.viewer._wwt.widget.page.runJavaScript("tourxml = '';", asynchronous=False)
E       TypeError: runJavaScript() got an unexpected keyword argument 'asynchronous'

on all Python 3.7+ tests although all the Qt* modules seem to be on the same versions as in the 3.6 envs.
The docs on https://www.riverbankcomputing.com/static/Docs/PyQt5/api/qtwebenginewidgets/qwebenginepage.html?highlight=runjavascript#methods do not mention any keyword args (or in fact document anything), so no idea for a possible substitute. Just leaving out the kwarg lets the save fail as well (#84).

To Reproduce
E.g CI runs on
https://dev.azure.com/glue-viz/glue-wwt/_build/results?buildId=2018&view=logs&j=a5e00f2a-e596-5064-edf3-1da4375679ea
Details:

• Operating System: [e.g. MacOS 10.13.2] all Linux and macOS versions on CI
• Python version (python --version): all Pythons 3.7-3.9
• Glue version (glue --version): [e.g. 0.14.5]
  – All tests in azure_pipelines
  Actually the test runs under Windows, where that test is skipped, do pass with

----------- coverage: platform win32, python 3.7.9-final-0 -----------
Coverage XML written to file D:\a\1\s\coverage.xml

================= 14 passed, 1 skipped, 61 warnings in 19.28s =================

but then hang indefinitely on finalising the Running tox step.