Fix broken lettuce tests

lms/djangoapps/courseware/features/problems.feature

@@ -113,9 +113,9 @@ Feature: Answer problems
     Scenario: I can view and hide the answer if the problem has it:
         Given I am viewing a "numerical" that shows the answer "always"
         When I press the button with the label "Show Answer(s)"
-        Then The "Hide Answer(s)" button does appear
-        And The "Show Answer(s)" button does not appear
+        Then the button with the label "Hide Answer(s)" does appear
+        And the button with the label "Show Answer(s)" does not appear
         And I should see "4.14159" somewhere in the page
         When I press the button with the label "Hide Answer(s)"
-        Then The "Show Answer(s)" button does appear
+        Then the button with the label "Show Answer(s)" does appear
         And I should not see "4.14159" anywhere on the page

lms/djangoapps/courseware/features/problems.py

@@ -126,6 +126,15 @@ def press_the_button_with_label(step, buttonname):
 
 @step(u'The "([^"]*)" button does( not)? appear')
 def action_button_present(step, buttonname, doesnt_appear):
+    button_css = 'section.action input[value*="%s"]' % buttonname
+    if doesnt_appear:
+        assert world.is_css_not_present(button_css)
+    else:
+        assert world.is_css_present(button_css)
+
+
+@step(u'the button with the label "([^"]*)" does( not)? appear')
+def button_with_label_present(step, buttonname, doesnt_appear):
     button_css = 'button span.show-label'
     elem = world.css_find(button_css).first
     if doesnt_appear: