CT: crashing with "Unexpected token < in JSON"

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While running CT (https://bayes.colorado.edu/continuous-testing/aqua/html/continuous-report.html), it’s periodically crashing. There's no useful stack trace. Here’s the console output:

...
aqua.min.js:1 Status: [11:00:00am] No changes; checking circuit-construction-kit-dc-virtual-lab
aqua.min.js:1 Status: [11:00:20am] No changes; checking collision-lab
aqua.min.js:1 Status: [11:00:49am] No changes; checking color-vision
aqua.min.js:1 GET https://bayes.colorado.edu/aquaserver/status 502 (Proxy Error)
VM48:1 Uncaught SyntaxError: Unexpected token < in JSON at position 0
    at JSON.parse (<anonymous>)
    at XMLHttpRequest.e.onload 

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Slack dev-public:

Jonathan Olson 11:15 AM
Likely looks like it timing out. Bayes seemed a bit slow when I logged on a few days ago. Is that a crash that affects usability?

Chris Malley 11:17 AM
It doesn’t seem to be able to get through a full cycle of the list without crashing. So yeah, I’d say that affects usability. And if it’s a timeout, that error message could use some work. Or add timeout handling.

Jonathan Olson 11:20 AM
“Crash” meaning “the interface fails after this”, or “a message is printed in the console”?

Chris Malley 11:23 AM
“Crash” meaning it hits an uncaught exception. I generally have “Pause on exceptions” enabled in Chrome dev tools. Not sure what happens if I turn if off for CT, maybe CT keeps running OK? And I have to remember to turn it off when running CT, then turn it back on when developing, which is a pain.