fix: Make the Ember tests pass again

Context: emberjs/ember-qunit#304

addon/instance-initializers/new-relic.js

@@ -17,7 +17,7 @@ export function initialize() {
     return errorName === 'TransitionAborted';
   }
 
-  function handleError(error) {
+  function handleError(error, shouldThrowError = true) {
     if (mustIgnoreError(error)) {
       return;
     }
@@ -28,6 +28,11 @@ export function initialize() {
       // Ignore
     }
 
+    // Ensure we don't throw errors with `Logger.error`
+    if (Ember.testing && shouldThrowError) {
+      throw error;
+    }
+
     console.error(error);
   }
 
@@ -44,7 +49,7 @@ export function initialize() {
   Ember.RSVP.on('error', handleError);
 
   Ember.Logger.error = function(...messages) {
-    handleError(generateError(messages.join(' ')));
+    handleError(generateError(messages.join(' ')), false);
   };
 }
 

tests/acceptance/new-relic-browser-test.js

@@ -10,7 +10,7 @@ test('Loading New Relic Browser', function(assert) {
   andThen(function() {
     var newRelic = window.NREUM;
 
-    assert.expect(8);
+    assert.expect(9);
 
     assert.ok(newRelic,
       'The New Relic object (NREUM) should be added to the window');
@@ -22,7 +22,6 @@ test('Loading New Relic Browser', function(assert) {
     caught by the extra Ember events like onerror */
 
     window.NREUM.noticeError = function(error) {
-
       assert.ok(true,
         'noticeError should be called by Ember.onerror');
 
@@ -33,22 +32,22 @@ test('Loading New Relic Browser', function(assert) {
         'noticeError should not be called by Ember.onerror on TransitionAborted errors.');
     };
 
-    Ember.onerror(new Error('Awh crap'));
+    assert.throws(() => {
+      Ember.onerror(new Error('Awh crap'));
+    }, 'Awh crap');
 
     const transitionError = new Error('Ember Transition Aborted Test');
     transitionError.name = "TransitionAborted";
     Ember.onerror(transitionError);
 
     Ember.Logger.error('Whoops', 'We done messed up', {});
-
   });
 });
 
 test('console.error from Ember.Logger.error correctly shows messages', function(assert) {
   visit('/');
 
   andThen(function() {
-
     console.error = function (message) {
       assert.strictEqual(
         message.toString(),