# emerge -uDN world -pv                                                                                                                   0:02:33

These are the packages that would be merged, in order:

Calculating world dependencies -Traceback (most recent call last):
  File "/usr/bin/emerge", line 5299, in ?
    retval = emerge_main()
  File "/usr/bin/emerge", line 5294, in emerge_main
    myopts, myaction, myfiles, spinner)
  File "/usr/bin/emerge", line 4614, in action_build
    if not mydepgraph.xcreate(myaction):
  File "/usr/bin/emerge", line 2169, in xcreate
    if not self.validate_blockers():
  File "/usr/bin/emerge", line 1942, in validate_blockers
    self.altlist()
  File "/usr/bin/emerge", line 2062, in altlist
    mygraph.remove(node)
  File "/usr/lib/portage/pym/portage.py", line 349, in remove
    raise KeyError(node)
KeyError: ('ebuild', '/', 'xfce-base/xfce-utils-4.4.0-r2', 'merge')