E3 fails uninformatively on missing data link

[karger]

When an exhibit includes any link to a nonexistent data file, even if other links are good, E3 issues a relatively opaque "uncaught exception: Not Found" message in the error console. Adding the faulty URL would be nice. More importantly, this kind of "fail fast" is good for programmers but I don't think it's ideal for non-users. I suggest that we take a lesson from the browser, which tries to proceed if e.g. it fails to load a script or an image. Exhibit should try to load any other data files, render the exhibit, etc. This will give the naive user more information about what's gone wrong, and may also produce something useful-though-imperfect. Summarizing: we should issue warning, not throw errors, for these kind of non-fatal issues.

See an example at http://people.csail.mit.edu/karger/Exhibit3/demos/nobelists/broken-nobelists.html