[Bug 1632047] [ubuntu-release-upgrader/xenial] possible regression found

[Ubuntu Foundations Team Bug Bot]

As a part of the Stable Release Updates quality process a search for
Launchpad bug reports using the version of ubuntu-release-upgrader from
xenial-proposed was performed and bug 1636237 was found.  Please
investigate this bug report to ensure that a regression will not be
created by this SRU. In the event that this is not a regression remove
the "verification-failed" tag from this bug report and add the tag "bot-
stop-nagging" to bug 1636237 (not this bug). Thanks!

** Tags added: verification-failed

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https://bugs.launchpad.net/bugs/1632047

Title:
  DistUpgradeViewNonInteractive except hook hides the traceback

Status in ubuntu-release-upgrader package in Ubuntu:
  Fix Released
Status in ubuntu-release-upgrader source package in Xenial:
  Fix Committed
Status in ubuntu-release-upgrader source package in Yakkety:
  Fix Released

Bug description:
  Test Case
  ---------
  This is a pretty obvious fix to just log more information when there is a crash.

  Regression Potential
  --------------------
  Little as we are just logging more information.

  The non-interactive version of the dist upgrade process has its own
  special except hook handler, but that handler ends up hiding the
  traceback.  This should be fixed so that we have more details about
  why the upgrade failed.  Here's the code in question:

  249 class DistUpgradeViewNonInteractive(DistUpgradeView):
  250     " non-interactive version of the upgrade view "
  251     def __init__(self, datadir=None, logdir=None):
  252         DistUpgradeView.__init__(self)
  253         self.config = DistUpgradeConfig(".")
  254         self._acquireProgress = NonInteractiveAcquireProgress()
  255         self._installProgress = NonInteractiveInstallProgress(logdir)
  256         self._opProgress = apt.progress.base.OpProgress()
  257         sys.__excepthook__ = self.excepthook
  258     def excepthook(self, type, value, traceback):
  259         " on uncaught exceptions -> print error and reboot "
  260         logging.exception("got exception '%s': %s " % (type, value))
  261         #sys.excepthook(type, value, traceback)
  262         self.confirmRestart()

  Notice nothing is done with traceback in line 260.

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