Intermittent test failures for test doesn't send 404 for known files (Obelisk.Plug.ServerTest)

[fahrradflucht]

  1) test doesn't send 404 for known files (Obelisk.Plug.ServerTest)
     test/plug/server_test.exs:18
     ** (File.Error) could not write file stats "/Users/Mathis/Desktop/obelisk/build/index.html": no such file or directory
     stacktrace:
       (elixir) lib/file.ex:358: File.write_stat!/3
       (elixir) lib/file.ex:645: File.do_cp_file/4
       (elixir) lib/enum.ex:1623: Enum."-reduce/3-lists^foldl/2-0-"/3
       (elixir) lib/file.ex:577: File.cp_r/3
       test/plug/server_test.exs:21: (test)

  1) test doesn't send 404 for known files (Obelisk.Plug.ServerTest)
     test/plug/server_test.exs:18
     Expected truthy, got false
     code: conn.halted()
     stacktrace:
       test/plug/server_test.exs:27: (test)