Still encountering this exact issue on CE 2.1.7.
Still in CE 2.1.8
sampledata:remove
gives the same error.
You can remove (or install) it manually by;
composer remove magento/sample-data-media magento/module-widget-sample-data magento/module-cms-sample-data magento/module-wishlist-sample-data magento/module-catalog-sample-data magento/module-tax-sample-data magento/module-sales-sample-data magento/module-sales-rule-sample-data magento/module-downloadable-sample-data magento/module-customer-sample-data magento/module-grouped-product-sample-data magento/module-msrp-sample-data magento/module-review-sample-data magento/module-catalog-rule-sample-data magento/module-configurable-sample-data magento/module-product-links-sample-data magento/module-swatches-sample-data magento/module-theme-sample-data magento/module-bundle-sample-data
Most helpful comment
Still encountering this exact issue on CE 2.1.7.