use a custom emitter to throw the error; then test for it

lib/dao-factory.js

@@ -789,6 +789,12 @@ module.exports = (function() {
       options = Utils._.extend(options, fieldsOrOptions)
     }
 
+    if(this.daoFactoryManager.sequelize.options.dialect === 'postgres' && options.ignoreDuplicates ) {
+      return new Utils.CustomEventEmitter(function(emitter) {
+        emitter.emit('error', new Error('Postgres does not support the \'ignoreDuplicates\' option.'))
+      }).run();
+    }
+
     var self          = this
       , updatedAtAttr = Utils._.underscoredIf(self.options.updatedAt, self.options.underscored)
       , createdAtAttr = Utils._.underscoredIf(self.options.createdAt, self.options.underscored)

lib/dialects/postgres/query-generator.js

@@ -268,10 +268,6 @@ module.exports = (function() {
     },
 
     bulkInsertQuery: function(tableName, attrValueHashes, options) {
-      if(options && options.ignoreDuplicates) {
-        throw new Error("Postgres does not support the 'ignoreDuplicates' option.")
-      }
-
       var query        = "INSERT INTO <%= table %> (<%= attributes %>) VALUES <%= tuples %> RETURNING *;"
         , tuples       = []
         , serials      = []

test/dao-factory/create.test.js

@@ -1021,10 +1021,14 @@ describe(Support.getTestDialectTeaser("DAOFactory"), function () {
 
         this.User.bulkCreate(data, { fields: ['uniqueName', 'secretValue'] }).success(function() {
           data.push({ uniqueName: 'Michael', secretValue: '26' });
-          self.User.bulkCreate(data, { fields: ['uniqueName', 'secretValue'], ignoreDuplicates: true }).success(function() {
-            expect(err.message).to.match(/Postgres does not support the 'ignoreDuplicates' option./);
-            done()
-          });
+
+          self.User.bulkCreate(data, { fields: ['uniqueName', 'secretValue'], ignoreDuplicates: true }).error(function(err) {
+            console.log('err?', err)
+            expect(err).to.exist
+            expect(err.message).to.match(/Postgres does not support the \'ignoreDuplicates\' option./)
+
+            done();
+          })
         })
       })
     }