FTP error handling

[farski]

Looking at ways that error reporting could be improved now that we're using waitForTaskToken on these tasks.

Given the example we saw recently of a TLS cert verification error preventing login,

• that raises an error (I assume an OpenSSL::SSL::SSLError error, we don't currently log the error class, but the message was SSL_connect returned=1 errno=0 peeraddr=XXX.xxx.XXX.xxx:21 state=error: certificate verify failed (self-signed certificate)), which we catch to log and then re-raise.
• The re-raised error gets caught, recorded, and increments attempt, and then goes back to the start of the while !result && (attempt <= max_attempts) loop
• Once attempts are exhausted, the loops exist and, since there is no result, we raise "FTP failed, no more retries: from '#{local_file}' to '#{cstr}'" (yields something like "Error": "RuntimeError", "Cause": "FTP failed, no more retries: from '#<File:0x00007f513f571123>' to 'ftps://tktk:*******@XXX.xxx.XXX.xxx:21/123456.wav'")
• That raised error is what is ultimately caught in ftp.rb and triggers sf.send_task_failure to declare the task a failure.

So the end result is that anytime we hit that final raise, we always get a RunTime error, regardless of the cause.

Could we do something to preserve the underlying issue better, so that when we get to the send_task_failure, it has some additional useful info? The error that causes send_task_failure is what gets included in the Porter task result callback and becomes visible to a client app, so it could be beneficial to preserve more info throughout the run.