This command isn't working when installing from a local tarball. For reasons which aren't entirely clear yet, `sourcefile` is a relative path and not in this directory (I'm not sure which of those is wrong, but obviously both should not be true at once). The big problem is that while `gzip -dc non-existent-file` will exit 1, `gzip -dc non-existent-file | tar xof -` will exit 0 (wat). So this carries on happily as if nothing went wrong (the later commands don't care that the directory is empty). It fails later when trying to read the metadata.json file, which obviously doesn't exist.