Don't log/comment errors, require an admin to look at the logs.

[maleadt]

We recently leaked our environment-specified tokens in the log by dumping a Process object, so this PR includes a commit that removes all error reporting from the log generation. Instead, we'll now just comment that the job has failed, and expect the admin to check the server logs. cc @vtjnash

[vtjnash]

Seems to make sense to me. We don't include enough info here to be useful, but too much could be more likely to risk printing a secret

[maleadt]

Exception objects also leaked in another code path, e.g. JuliaLang/julia#46075 (comment), so I removed that and streamlined the error reporting. The run methods can now just throw, and only the server will catch those exceptions and turn them into a generic something failed error. This also makes it more reliable to execute the run methods during testing, where previously they wouldn't actually error but only generate a log with errors in them.