Just to let you all know, moodle.org has recently been upgraded and is now running 3.0rc2.If you notice any problems, please let us know either by posting here or by creating a Moodle Community Sites issue in the Moodle Tracker.
"Can't Read Database"
I notice that Matteo has commented about the problem in MDL-29738. Please feel free to create a new issue if you think it necessary.
This is because of the shift to template-ised emails in 3.0.
I've pushed a fix in MDL-52126 but I haven't got any time tonight to finish the issue with testing instructions, etc.
This is nothing to do with the (deliberately) empty head section of the e-mails.
There may be a further issue with the HTML template - I'll take a look at this tomorrow if no-one else has looked into it by then.