Changed error message on failure and made test more robust

Better error message

cms/djangoapps/contentstore/features/common.py

@@ -265,9 +265,8 @@ def type_in_codemirror(index, text):
 
 
 def upload_file(filename):
-    file_css = '.upload-dialog input[type=file]'
-    upload = world.css_find(file_css).first
     path = os.path.join(TEST_ROOT, filename)
-    upload._element.send_keys(os.path.abspath(path))
+    world.browser.execute_script("$('input.file-input').css('display', 'block')")
+    world.browser.attach_file('file', os.path.abspath(path))
     button_css = '.upload-dialog .action-upload'
     world.css_click(button_css)

cms/djangoapps/contentstore/features/course-settings.py

@@ -168,15 +168,18 @@ def i_see_new_course_image(_step):
     img = images[0]
     expected_src = '/c4x/MITx/999/asset/image.jpg'
     # Don't worry about the domain in the URL
-    assert img['src'].endswith(expected_src)
+    try:
+        assert img['src'].endswith(expected_src)
+    except AssertionError as e:
+        e.args += ('Was looking for {}'.format(expected_src), 'Found {}'.format(img['src']))
+        raise
 
 
 @step('the image URL should be present in the field')
 def image_url_present(_step):
     field_css = '#course-image-url'
-    field = world.css_find(field_css).first
     expected_value = '/c4x/MITx/999/asset/image.jpg'
-    assert field.value == expected_value
+    assert world.css_value(field_css) == expected_value
 
 
 ############### HELPER METHODS ####################