Fix getFeature() semantics

It will always reject if the feature is not found, not resolve to null.

lib/featureApi.js

@@ -11,13 +11,11 @@ module.exports = function (app) {
     });
 
     app.get('/features/:featureName', function (req, res) {
-        featureDb.getFeature(req.params.featureName).then(function (feature) {
-            if (feature) {
-                res.json(feature);
-            } else {
+        featureDb.getFeature(req.params.featureName)
+            .then(function (feature) { res.json(feature); })
+            .catch(function () {
                 res.status(404).json({error: 'Could not find feature'});
-            }
-        });
+            });
     });
 
     app.post('/features', function (req, res) {
@@ -34,7 +32,11 @@ module.exports = function (app) {
         var newFeature = req.body;
 
         var handleFeatureExist = function() {
-            res.status(403).end();
+            var errors = [
+                {msg: "A feature named '" + newFeature.name + "' already exists."}
+            ];
+
+            res.status(403).json(errors).end();
         };
 
         var handleCreateFeature = function () {
@@ -49,7 +51,9 @@ module.exports = function (app) {
             });
         };
 
-        featureDb.getFeature(newFeature.name).then(handleFeatureExist, handleCreateFeature);
+        featureDb.getFeature(newFeature.name)
+            .then(handleFeatureExist)
+            .catch(handleCreateFeature);
     });
 
     app.put('/features/:featureName', function (req, res) {

lib/featureDb.js

@@ -31,20 +31,17 @@ function getFeatures() {
 
 function getFeature(name) {
     return knex
-        .select(FEATURE_COLUMNS)
+        .first(FEATURE_COLUMNS)
         .from('features')
         .where({name: name})
-        .limit(1)
-        .then(function (rows) {
-            if (rows.length) {
-                return rowToFeature(rows[0]);
-            } else {
-                throw new Error('could not find feature named: ' + name);
-            }
-        });
+        .then(rowToFeature);
 }
 
 function rowToFeature(row) {
+    if (!row) {
+        throw new Error('invalid row');
+    }
+
     return {
         name: row.name,
         description: row.description,