Hi,
I got the same error as well, its very frustrating.
I deleted the whole of the WP installation, and started installation from beginning.
I successfully installed the theme, after that I started with the plugins one by one and when I reached to the revolution slider, I was able to successfully install it but when I activate it I get this error: The plugin generated unexpected output. (Image attachment 1).
I then continued to install all other plugins and didnt face any problem installing YITH WooCommerce Wishlist, in contrast to my first trial.
But when I clicked Appearance -> Theme, I got the above error. Now I have re-do everything all over again.
This time I installed the child theme, and when running through all steps above until I reach to installing the plugin of Revolution Slider I get the following error:
Downloading install package from /home1/gialady/public_html/wp-content/themes/neighborhood-child/includes/plugins/revslider.zip…
Download failed. A valid URL was not provided.
There I opted to upload the file manually, the plugin installed successfully but, when activating I got the error above (image error 1 attached). How frustrating!
This, I installed all plugins and kept the revolution slider till the end, but unfortunately as usual upon activating I got the following error again:
Fatal error: Call to a member function get_page_permastruct() on a non-object in /home1/gialady/public_html/wp-includes/link-template.php on line 271
I urge you to help in solving this problem, as I am on a tight deadline to complete the site.
Thanks, AJ