Fix broken links etc

[duck-rh]

Quack,

As found out with the recently added CI there are broken links and other problems: https://github.com/pulp/pulpproject.org/runs/4854825455?check_suite_focus=true

Like links towards http://website-pulp.rhcloud.com/wp-content/uploads/ which aside from not using HTTPS is a broken link. Is there a way to get back those assets (in a backup maybe)? or should we simply get rid of these links?

The goal is to fix all these problems and make the check compulsory. I can prepare a PR but it would help to get some direction as I don't know the content as well as you.
\_o<

[melcorr]

Quack @duck-rh !
Thank you for all your efforts with this.
Looking at where the errors are, all of this looks pretty old. I think we could remove these broken links with relative safety.

[KevinMGranger]

The link to "writing a plugin" on the content plugins page is broken. It points to https://docs.pulpproject.org/pulpcore/plugins/plugin-writer/index.html which is returning a 404.

I believe the correct url is https://docs.pulpproject.org/pulpcore/plugin_dev/index.html.