Comment by Animats

Here's Google, complaining of problems with pages they want to index but I blocked with robots.txt.

    New reason preventing your pages from being indexed

    Search Console has identified that some pages on your site are not being indexed 
    due to the following new reason:

        Indexed, though blocked by robots.txt

    If this reason is not intentional, we recommend that you fix it in order to get
    affected pages indexed and appearing on Google.
    Open indexing report
    Message type: [WNC-20237597]