If you are a WordPress user you may have experienced the above error when trying to update themes (or any other WordPress plugin, for that matter).
Update Failed: The update cannot be installed because we will be unable to copy some files. This is usually due to inconsistent file permissions.
In most cases, the issue is caused by the incorrect file permissions on your server. Basically, WordPress unable to properly access its own themes or plugins directory, and as a result, it failed to put the newly updated files over there.
Solve the problem by making apache as the owner
sudo chown -R www-data:www-data /var/www
Okay now, the issue should have been resolved, if all is well, you will be able to update the plugin successfully in the WordPress plugins listing.
Make sure that the “wp-content/” and “wp-content/plugins/” directories are set to the recommended permissions. see recommended wordpress file permissions.
If you’re not comfortable doing this yourself, your web host may be able to make the necessary permissions changes for you.