hg exited with non-zero status: 255

I'm unable to browse the repository for a project. I've tried removing the repository, cloning again and restarting the server. The repository used to work, so a recent commit must have broken it somehow.

The errormassge reads: An error occurred when trying to access the repository: hg exited with non-zero status: 255

The log just says Compleded 500 Internal Server Errer in ...ms ...