Intermittent test failures for test sends file if exists (Obelisk.Plug.IndexTest)

[fahrradflucht]

  1) test sends file if exists (Obelisk.Plug.IndexTest)
     test/plug/index_test.exs:30
     ** (File.Error) could not read file stats "/Users/Mathis/Desktop/obelisk/build/index.html": no such file or directory
     stacktrace:
       (elixir) lib/file.ex:289: File.stat!/2
       (plug) lib/plug/adapters/test/conn.ex:43: Plug.Adapters.Test.Conn.send_file/6
       (plug) lib/plug/conn.ex:349: Plug.Conn.send_file/5
       (obelisk) lib/obelisk/plug/index.ex:21: Obelisk.Plug.Index.call/2
       test/plug/index_test.exs:37: (test)