make compare pixel test runner aware of plotly.js errors
make compare pixel test runner aware of plotly.js errors

... when generating image, instead of hanging with no logs.

asolagmbh/plotly.js,asolagmbh/plotly.js,aburato/plotly.js,iongroup/plotly.js,plotly/plotly.js,aburato/plotly.js,asolagmbh/plotly.js,etpinard/plotly.js,plotly/plotly.js,iongroup/plotly.js,iongroup/plotly.js,etpinard/plotly.js,plotly/plotly.js,etpinard/plotly.js,plotly/plotly.js