Remove enum34 package from output_template

[kchygoe]

Blueoil inference doesn't work with python2 any longer. We need to update the pip packages for inference but enum34 package would be the block for some recent packages. Now the CI has pip uninstall enum34 in the pipeline for the test backward compatibility, but this is no longer required for future.

Related to https://github.com/blue-oil/blueoil/pull/1139