Use has_trace? instead of case switch, feedback:

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7617#note_18745170

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7617#note_18745221

app/models/generic_commit_status.rb

@@ -12,4 +12,8 @@ class GenericCommitStatus < CommitStatus
   def tags
     [:external]
   end
+
+  def has_trace?
+    false
+  end
 end

app/views/notify/pipeline_failed_email.html.haml

@@ -165,12 +165,11 @@
                                       - when GenericCommitStatus
                                         = build.name
                                   %tr.build-log
-                                    - case build
-                                    - when Ci::Build
+                                    - if build.has_trace?
                                       %td{colspan: "2", style: "font-family:'Helvetica Neue',Helvetica,Arial,sans-serif;padding:0 0 15px;"}
                                         %pre{style: "font-family:Monaco,'Lucida Console','Courier New',Courier,monospace;background-color:#fafafa;border-radius:3px;overflow:hidden;white-space:pre-wrap;word-break:break-all;font-size:13px;line-height:1.4;padding:12px;color:#333333;margin:0;"}
                                           = build.trace_html(last_lines: 10).html_safe
-                                    - when GenericCommitStatus
+                                    - else
                                       %td{colspan: "2"}
         %tr.footer
           %td{style: "font-family:'Helvetica Neue',Helvetica,Arial,sans-serif;padding:25px 0;font-size:13px;line-height:1.6;color:#5c5c5c;"}

app/views/notify/pipeline_failed_email.text.erb

@@ -22,7 +22,7 @@ Pipeline #<%= @pipeline.id %> ( <%= pipeline_url(@pipeline) %> ) had <%= failed.
 Build #<%= build.id %><%= if build.kind_of?(Ci::Build) then " ( #{pipeline_build_url(@pipeline, build)} )" end %>
 Stage: <%= build.stage %>
 Name: <%= build.name %>
-<% if build.kind_of?(Ci::Build) -%>
+<% if build.has_trace? -%>
 Trace: <%= build.trace_with_state(last_lines: 10)[:text] %>
 <% end -%>