From the point of view of making tooling that interacts with this project it would be easier to deal with a missing log file if the following code had a 404 response when there's no log file instead of having to look at the contents of the returned text.
https://github.com/CoEDL/elpis/blob/913c567bfaafc2081bc96fbd80036b07d4762bf0/elpis/endpoints/__init__.py#L26-L33
From the point of view of making tooling that interacts with this project it would be easier to deal with a missing log file if the following code had a 404 response when there's no log file instead of having to look at the contents of the returned text.