Bug#1126222: #1126222 pandas: read_html(flavor=bs4) broken with pyside2

[Rebecca N. Palmer]

Control: retitle -1 pandas: read_html(flavor=bs4) broken with pyside2

This seems to be happen when the tests are run with pyside2 (because of 
#112*5*222) instead of pyqt5.

I don't know how, given that the traceback doesn't involve Qt at all, 
but it implies that PYTEST_QT_API=pyqt5 (as in Salsa) is at least a 
workaround.  (I'm not calling it a full fix because I'm not sure if 
pandas is supposed to work with pyside, i.e. whether it's a bug in 
itself that it doesn't.)