I’m ugrading from v2.6.0.beta4 +52
When I arrived to upgrade I found everything still upgrading from the last time … except the docker manager?
I reset all and started to upgrade Docker … this is the where it all went pear-shaped.
rake aborted!
Don't know how to build task 'themes:update' (See the list of available tasks with `rake --tasks`)
Did you mean? themes:audit
/var/www/discourse/vendor/bundle/ruby/2.6.0/gems/rake-13.0.1/exe/rake:27:in `<top (required)>'
I tried again.
When I noticed ‘themes:update’ I upgraded two theme components.
When I returned to check on the Docker upgrade it had successfully completed.
Not sure if my upgrading the theme components was the fix.
But it had failed to upgrade twice before I did it.
@geoff777 Thank you for posting how you solved the problem! May I ask how does one upgrade themes and components? I have the same error but I only have two stock themes and no components at all. How do I install a Theme or Theme Component? does not describe any specifics of theme updates, only a way to install them from git. Did you have to overwrite the stock theme with the latest version from github?
2.6.0.beta4 to 2.7.0.beta1 in my case.
P.S. My guess is that you used https://github.com/discourse/discourse/blob/b5705348b32fff406d8e7e3463def65eaf635206/lib/tasks/themes.rake but I am not sure how to invoke it correctly to keep my install “upgradeable” (I don’t want to install any customizations).
Hi Andrew,
I have a few theme components installed. Two needed updating.
I wasn’t sure whether my updating the theme components was the reason everything started to work.
I think it’s just the old computer gremlins … no explanation why but it worked the third time and thank you … move on before it breaks again … 
Had a similar error, and the UI claims my themes are up to date. Not sure how to proceed. Also updating 2.6 to 2.7
Can you try a rebuild?
cd /var/discourse
./launcher rebuild app
yep, I’ll try that next.
That fixed it, thanks.