fix(scenario): include error messages in XML output

Fix the XML output of scenario tests so that it properly includes error
messages from failing specs.

src/ngScenario/output/Xml.js

@@ -43,7 +43,7 @@ angular.scenario.output('xml', function(context, runner, model) {
          if (step.error) {
            var error = $('<error></error>');
            stepContext.append(error);
-           error.text(formatException(stepContext.error));
+           error.text(formatException(step.error));
          }
        });
      });

test/ngScenario/output/xmlSpec.js

@@ -1,6 +1,6 @@
 'use strict';
 
-describe('angular.scenario.output.json', function() {
+describe('angular.scenario.output.xml', function() {
   var output, context;
   var runner, model, $window;
   var spec, step;
@@ -33,4 +33,17 @@ describe('angular.scenario.output.json', function() {
     expect(context.find('it').attr('status')).toEqual('success');
     expect(context.find('it step').attr('status')).toEqual('success');
   });
+
+  it('should output errors to the XML', function() {
+    runner.emit('SpecBegin', spec);
+    runner.emit('StepBegin', spec, step);
+    runner.emit('StepFailure', spec, step, 'error reason');
+    runner.emit('StepEnd', spec, step);
+    runner.emit('SpecEnd', spec);
+    runner.emit('RunnerEnd');
+
+    expect(context.find('it').attr('status')).toEqual('failure');
+    expect(context.find('it step').attr('status')).toEqual('failure');
+    expect(context.find('it step').text()).toEqual('error reason');
+  });
 });