Comment 2 for bug 1598310

I am marking verification-done, as this fixes the issue for me on xenial.

When running with the curtin build currently in xenial-updates (/dev/vdb3 is used as physical volume for several lvm volumes):

  root@ubuntu:/home/ubuntu# apt-cache policy curtin
    curtin:
      Installed: 0.1.0~bzr399-0ubuntu1~16.04.1
      Candidate: 0.1.0~bzr399-0ubuntu1~16.04.1
  root@ubuntu:/home/ubuntu# python3
    Python 3.5.2 (default, Sep 10 2016, 08:21:44)
    [GCC 5.4.0 20160609] on linux
    Type "help", "copyright", "credits" or "license" for more information.
    >>> from curtin import block
    >>> block.get_blockdev_sector_size("/dev/vdb3")
      Traceback (most recent call last):
         File "<stdin>", line 1, in <module>
         File "/usr/lib/python3/dist-packages/curtin/block/__init__.py", line 426, in get_blockdev_sector_size
           [parent] = info
      ValueError: too many values to unpack (expected 1)

When running with proposed (note that 4096 is actual sector size as advanced format disk used):

  root@ubuntu:/home/ubuntu# apt-cache policy curtin
    curtin:
      Installed: 0.1.0~bzr425-0ubuntu1~16.04.1
      Candidate: 0.1.0~bzr425-0ubuntu1~16.04.1

  root@ubuntu:/home/ubuntu# python3
    Python 3.5.2 (default, Sep 10 2016, 08:21:44)
    [GCC 5.4.0 20160609] on linux
    Type "help", "copyright", "credits" or "license" for more information.
    >>> from curtin import block
    >>> block.get_blockdev_sector_size("/dev/vdb3")
      (4096, 4096)