Error class handlers and logger print (unexpected) errors in Websocket middleware

[emschwartz]

While working on getting two ledgers and a connector set up, @dappelt found the following issues:

Both our error classes and koa-riverpig assume that they are being used in a normal Koa context. However, when combined with koa-websocket (as in here), the this value normally set by koa is instead undefined. In both cases, it seems that an error is logged (with debug so you need DEBUG=* to see it) but the app continues running so it's not critical but they should probably be fixed nonetheless.

For the error classes, an (unexpected) error is logged when the handler tries to set properties on the context here. You should be able to reproduce this by trying to subscribe to transfers for an account that doesn't exist.

In koa-riverpig, there is a similar problem where it tries to access fields on the koa context without checking if they exist. This appears to happen whenever you subscribe to an account that does exist. The specific error printed is:

2016-11-09T14:22:49.251Z koa:websocket debug TypeError: Cannot read property 'once' of undefined
   at Object.logMiddleware (.../five-bells-ledger/node_modules/koa-riverpig/dist/src/index.js:60:12)