Fix spinach test

features/project/network_graph.feature

@@ -43,4 +43,4 @@ Feature: Project Network Graph
   Scenario: I should fail to look for a commit
     When I look for a commit by ";"
-    Then page status code should be 404
+    Then I should see non-existent git revision error message

features/steps/project/network_graph.rb

@@ -109,4 +109,8 @@ class Spinach::Features::ProjectNetworkGraph < Spinach::FeatureSteps
       find('button').click
     end
   end
+
+  step 'I should see non-existent git revision error message' do
+    expect(page).to have_selector '.flash-alert', text: "Git revision ';' does not exist."
+  end
 end