I'm trying to override the admin theme for user/%/edit pages. I first set a themekey rule for that path to use my default theme, but I saw the message that "Seven is the admin theme, which is stronger than themekey rules." So I set admin theme to "default". In themekey rules, everywhere I had referenced "=> Administration theme", I changed it to Seven. Then I added a rule for path_is_admin and also specified Seven. I get an error stating "Theme is not activated." [it would be helpful if the error message gave the theme name.]
When I go to admin pages, I see my default theme, not Seven.