swallow error for automatic rollback

lib/datastore/transaction.js

@@ -200,19 +200,10 @@ Transaction.prototype.commit = function(callback) {
   this.request_(protoOpts, reqOpts, function(err, resp) {
     if (err) {
       // Rollback automatically for the user.
-      self.rollback(function(err) {
-        if (err) {
-          err.message = [
-            'The commit was not successful and the transaction could not be',
-            'rolled back. You may want to try calling transaction.rollback().',
-            '\n',
-            '\n',
-            err.message
-          ].join('');
-        }
-
-        // Provide the response items from the failed commit to the user. A
-        // successful rollback should be transparent.
+      self.rollback(function() {
+        // Provide the response items from the failed commit to the user. Even
+        // a failed rollback should be transparent.
+        // RE: https://github.com/GoogleCloudPlatform/gcloud-node/pull/1369#discussion_r66833976
         callback(err, resp);
       });
       return;

test/datastore/transaction.js

@@ -161,15 +161,27 @@ describe('Transaction', function() {
       transaction.commit(done);
     });
 
-    it('should pass error to callback', function(done) {
+    describe('errors', function() {
       var error = new Error('Error.');
-      transaction.request_ = function(protoOpts, reqOpts, callback) {
-        callback = callback || reqOpts;
-        callback(error);
-      };
-      transaction.commit(function(err) {
-        assert.deepEqual(err, error);
-        done();
+      var apiResponse = {};
+
+      beforeEach(function() {
+        transaction.rollback = function(callback) {
+          callback();
+        };
+
+        transaction.request_ = function(protoOpts, reqOpts, callback) {
+          callback = callback || reqOpts;
+          callback(error, apiResponse);
+        };
+      });
+
+      it('should pass the error to the callback', function(done) {
+        transaction.commit(function(err, resp) {
+          assert.strictEqual(err, error);
+          assert.strictEqual(resp, apiResponse);
+          done();
+        });
       });
     });