If I had to guess the install routine is not fetching the youtube-dl distribution files to install.
I get this error message Error: Failed to install youtube-dl: no destroot found at: /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_net_youtube-dl/youtube-dl/work/destroot-- Any help appreciated. ent- XR