The maintainer traced it to process.stdout.columns being undefined on CI and pushed a fix that landed in Portman 1.8.0. Upgrade, or as a workaround ensure the CI step allocates a TTY/column width.

Context: GitHub issue on apideck-libraries/portman: running Portman on CircleCI throws RangeError: Invalid count value. Root cause: some CI environments report no (or a tiny) stdout column width, and the column-formatting code choked on it.