This patch fixes the swollowing of the actual error message that appears when a file fails to move, after being uploaded to Hedgedoc on an instance that is using the upload-method `filesystem` active. This became apparent when the error messages provided by some users, where less than helpful. As a solution the error message of the copy command was added to the error that is output to the console. https://community.hedgedoc.org/t/image-upload-fail-docker/439 Signed-off-by: Sheogorath <sheogorath@shivering-isles.com>