All the builds fail consistently after http://buildbot.python.org/all/#/builders/54/builds/465 and things were passing before 465. Maybe is this something to do with the commit that happened there that we could revert and test it in the machine by doing a git-bisect? But I couldn't see anything on GDB related code being changed in Python on #465. My initial hunch was that it had something to do with GDB 8.0+ but Ubuntu 18.04 LTS also runs on 8.0+ fine.

Tests pass : 00e05242ae650bc29e8052a5fb79cbb83224a657
Tests fail : d6a283b37b66ecd2d0ff43602ddc8e91b54a51c5

➜  cpython git:(master) git log 00e05242ae650bc29e8052a5fb79cbb83224a657~1..d6a283b37b66ecd2d0ff43602ddc8e91b54a51c5

commit d6a283b37b66ecd2d0ff43602ddc8e91b54a51c5
Author: Zackery Spytz <zspytz@gmail.com>
Date:   Fri Jun 29 13:30:07 2018 -0600

    [3.6] bpo-25862: Fix assertion failures in io.TextIOWrapper.tell(). (GH-3918). (GH-8012)

    (cherry picked from commit 23db935bcf258657682e66464bf8512def8af830)

    Co-authored-by: Zackery Spytz <zspytz@gmail.com>

commit a73027918a659ca69480a7e023d3838e2601ce6d
Author: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>
Date:   Fri Jun 29 03:17:43 2018 -0700

    Fix the indentation in the documentation of bin() and hash() (GH-7998)

    (cherry picked from commit bda9c3eae3ad16e43145599ac6359bfdcaf1fd4a)

    Co-authored-by: Andrés Delfino <adelfino@gmail.com>

commit 00e05242ae650bc29e8052a5fb79cbb83224a657
Author: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>
Date:   Thu Jun 28 22:32:16 2018 -0700

    bpo-14117: Make minor tweaks to turtledemo (GH-8002)


    The 'wikipedia' example is now 'rosette', describing what it draws.
    The 'penrose' print output is reduced.  The 'tree' '1024'
    output is eliminated.
    (cherry picked from commit 891a1f86d415779cf67ca23e626a868e586feb05)

    Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>