Failed to register device: landscape.client.broker.registr ation.RegistrationHandler

[ Impact ]

 * Landscape-client fails to start on some hardware where the DMI fields
   for chassis/bios/product are invalid utf-8.

 * This prevents some machines from being managed by landscape on bionic.
   The issue has already been patched on following series. Previous series
   were relying on python2 str and were comparing binary data, thus are
   also unaffected.

[ Test Plan ]

 * apt install cloud-image-utils qemu-system-x86

 * wget http://cloud-images.ubuntu.com/bionic/current/bionic-server-cloudimg-amd64.img

 * printf '#cloud-config\npassword: ubuntu\nchpasswd:\n expire: False\npackages:\n- landscape-client' | cloud-localds seed.img -

 * kvm -smbios type=3,manufacturer=$'\xff' \
   -smbios type=1,manufacturer=$'\xff' -snapshot \
   -drive file=bionic-server-cloudimg-amd64.img,if=virtio \
   -drive file=seed.img,if=virtio -m 2G -nic user,hostfwd=tcp::2222-:22

 * ssh -p 22222 localhost with ubuntu:ubuntu

 * sudo landscape-config -a account -p registrationkey \
   -t my_bad_dmi_machine --silent

 * check /var/log/landscape/broker.log for decoding errors

[ Where problems could occur ]

 * The backported patch touches a few code paths related to file reading.
   In particular, the now lossy decoding (due to decode replace)
   could have the side effect of unblocking code paths which previously
   were failing early on the decoding. This could surface in new errors
   in code which now gets to execute on affected machines.

 * The lossy decoding now introduces some utf8 replacement characters.
   That replacement character being unicode might generate some
   inconsistency if different code paths decode the same file data
   differently.

 * Also, that replacement character is non-ascii unicode. Although the
   server and clients should handle that gracefully, there is a chance
   that they never got to exercise some fields having unicode. This might
   surface more encoding issues in other parts of the code.