Allow 'error' prefix

[bengl]

Prior to this commit, any time you'd log something with 'error' as the prefix, it would give something like:

$ node -e "require('npmlog').error('error', 'some kind of error message')"

events.js:87
      throw Error('Uncaught, unspecified "error" event.');
            ^
Error: Uncaught, unspecified "error" event.
    at Error (native)
    at EventEmitter.emit (events.js:87:13)
    at EventEmitter.<anonymous> ($PWD/node_modules/npmlog/log.js:151:22)
    at EventEmitter.<anonymous> ($PWD/node_modules/npmlog/log.js:223:21)
    at [eval]:1:19
    at Object.exports.runInThisContext (vm.js:74:17)
    at Object.<anonymous> ([eval]-wrapper:6:22)
    at Module._compile (module.js:460:26)
    at evalScript (node.js:431:25)
    at startup (node.js:90:7)

This is because when there's a prefix, an event is emitted with the prefix as its type, and 'error'-type events are treated in a special way.

The quick and easy fix is to add a dummy event listener for 'error', so that's what I've done here. Plus a test.

The (reasonable, I think) side effect here is that it that emitted errors won't get thrown on their own.

[gr2m]

We've run into the same problem. Is there a reason why we can't merge this besides the failing tests?

[othiym23]

This is probably fine to land, but it's going to be a semver-major change (which is no problem for npm, because same maintainers etc) because it's possible somebody was relying on the old behavior. For some reason. 🎉

[gr2m]

This is probably fine to land, but it's going to be a semver-major change (which is no problem for npm, because same maintainers etc) because it's possible somebody was relying on the old behavior. For some reason. 🎉

I love this very much 💐 💞 #teamSemanticRelease #teamGreenkeeper

[othiym23]

Landed as d6b2162, will be released as npmlog@2 as soon as Travis goes green. Thanks, Bryan!

[bengl]

🎅

[gr2m]

yay 😃🐼