Note that there is still an issue somewhere. The first time users refresh to a snap using gtk-common-themes, they get the following error message:
error: cannot perform the following tasks:
- Download snap "gtk-common-themes" (319) from channel "stable" (rename /var/lib/snapd/snaps/gtk-common-themes_319.snap.partial /var/lib/snapd/snaps/gtk-common-themes_319.snap: no such file or directory)
- Download snap "gtk-common-themes" (319) from channel "stable" (rename /var/lib/snapd/snaps/gtk-common-themes_319.snap.partial /var/lib/snapd/snaps/gtk-common-themes_319.snap: no such file or directory)
Despite this error message, the refresh seems to succeed. However, some users are reporting that gtk-common-themes is still not installed: Auto-connect doesn't seem to work on refresh and the original issue: https://github.com/ubuntu/gtk-communitheme/issues/354#issuecomment-401633857