fixes #7979 - adding better error reporting for repo enable ui

[jlsherrill]

This adds better messages for:

• Fetching the list of available repositories for a repo set
• Enabling a repo

[ehelms]

What about putting the error_message text into a <pre></pre> to offset it a little more from the initial text? Should make copy/pasting the actual error message easier as well if a use rneeds to.

[ehelms]

When I drilled down to enabling an actual repository I ended up with a link to /foreman_tasks/dynflow. While when it failed enabling a repository set it provided me a proper task link.

[jlsherrill]

@ehelms correct, there's not really a way for us to grab the task due to the way the code is structured. I didn't want to re-write the enable repo task just for this legacy page.

[ehelms]

@jlsherrill That's fine, but it's redirecting me to '/foreman_tasks/dynflow' which may not be enabled in all cases?

[jlsherrill]

ohhhh right, that should be /foreman_tasks/tasks/ will fix

[jlsherrill]

@ehelms updated link to tasks list and put error in pre tag

[ehelms]

ACk