I'm getting 500 HTTP errors when I try to start a bisect on the chromeperf dashboard (e.g, [1] and [2]).

When I click the bisect button I get the following errors in the console:
  Failed to load resource: the server responded with a status of 500 ()
  simple_xhr.html:65 POST 
  https://chromeperf.appspot.com/pinpoint/new/bisect 500 ()
    send	@	simple_xhr.html:65
    Promise	@	simple_xhr.html:71
    asPromise	@	simple_xhr.html:70
    onCreateJob	@	pinpoint-job-dialog.html:154
    handler	@	polymer.html:507


[1] https://chromeperf.appspot.com/group_report?bug_id=818707
[2] https://chromeperf.appspot.com/group_report?bug_id=818695