Fix StudentLoginModal crash on invalid login

Add test for student bad login

app/views/courses/StudentLogInModal.coffee

@@ -26,10 +26,9 @@ module.exports = class StudentLogInModal extends ModalView
     data = forms.formToObject @$el
     @enableModalInProgress(@$el)
     auth.loginUser data, (jqxhr) =>
-      error = jqxhr.responseJSON[0]
-      message = _.filter([error.property, error.message]).join(' ')
-      if message is 'Missing credentials'
-        message = 'Enter both username and password'
+      message = jqxhr.responseText
+      if jqxhr.status is 401
+        message = 'Wrong username or password. Try again!'
         # TODO: Make the server return better error message
       message = _.string.capitalize(message)
       @disableModalInProgress(@$el)

test/app/views/courses/StudentLogInModal.spec.coffee

@@ -0,0 +1,22 @@
+StudentLoginModal = require 'views/courses/StudentLogInModal'
+RecoverModal = require 'views/core/RecoverModal'
+auth = require 'core/auth'
+
+describe 'StudentLoginModal', ->
+  
+  modal = null
+  
+  beforeEach ->
+    modal = new StudentLoginModal()
+    modal.render()
+
+  afterEach ->
+    modal.stopListening()
+
+  it 'displays an error when you submit an empty login form', ->
+    spyOn(auth, 'loginUser').and.callFake (data, callback) ->
+      callback { status: 401, responseText: "Unauthorized" }
+    modal.$el.find('#log-in-btn').click()
+    expect(modal.$el.html()).toContain('Wrong username or password. Try again!')
+    
+    jasmine.demoModal(modal)