Raise an exception if creating a test repository fails

spec/factories/projects.rb

@@ -38,7 +38,7 @@ FactoryGirl.define do
 
     trait :empty_repo do
       after(:create) do |project|
-        project.create_repository
+        raise "Failed to create repository!" unless project.create_repository
 
         # We delete hooks so that gitlab-shell will not try to authenticate with
         # an API that isn't running
@@ -48,7 +48,7 @@ FactoryGirl.define do
 
     trait :broken_repo do
       after(:create) do |project|
-        project.create_repository
+        raise "Failed to create repository!" unless project.create_repository
 
         FileUtils.rm_r(File.join(project.repository_storage_path, "#{project.path_with_namespace}.git", 'refs'))
       end