Description of problem:
Groups handling is broken in the current yum release.
It does many strange things. In the "Steps to reproduce" I'll only list a couple.

Version-Release number of selected component (if applicable):
yum-3.4.3-81.fc19.noarch
yum-3.4.3-83.fc19.noarch

How reproducible:
=================
Consistently, installing and removing groups.

Steps to Reproduce:
===================
1. yum groupupdate "MATE Desktop"
-> Warning: environment MATE Desktop does not exist.

2. yum groupupdate MATE
-> Attenzione: il gruppo mate-desktop non contiene alcun pacchetto da installare.

3. yum upgrade | grep -i mate
---> Pacchetto mate-file-manager.i686 0:1.6.0-1.fc19 settato per essere aggiornato
---> Pacchetto mate-file-manager.i686 0:1.6.1-1.fc19 settato per essere un aggiornamento
---> Pacchetto mate-file-manager-extensions.i686 0:1.6.0-1.fc19 settato per essere aggiornato
---> Pacchetto mate-file-manager-extensions.i686 0:1.6.1-1.fc19 settato per essere un aggiornamento
---> Pacchetto mate-netspeed.i686 0:1.5.2-1.fc19 settato per essere aggiornato
---> Pacchetto mate-netspeed.i686 0:1.6.0-1.fc19 settato per essere un aggiornamento
---> Pacchetto mate-power-manager.i686 0:1.6.0-1.fc19 settato per essere aggiornato
---> Pacchetto mate-power-manager.i686 0:1.6.0-2.fc19 settato per essere un aggiornamento

2. yum remove @mate-desktop
Plugin abilitati:fastestmirror, langpacks, priorities, remove-with-leaves, upgrade-helper, verify
Traceback (most recent call last):
  File "/bin/yum", line 29, in <module>
    yummain.user_main(sys.argv[1:], exit_code=True)
  File "/usr/share/yum-cli/yummain.py", line 316, in user_main
    errcode = main(args)
  File "/usr/share/yum-cli/yummain.py", line 126, in main
    result, resultmsgs = base.doCommands()
  File "/usr/share/yum-cli/cli.py", line 520, in doCommands
    return self.yum_cli_commands[self.basecmd].doCommand(self, self.basecmd, self.extcmds)
  File "/usr/share/yum-cli/yumcommands.py", line 852, in doCommand
    ret = base.erasePkgs(extcmds, pos=pos, basecmd=basecmd)
  File "/usr/share/yum-cli/cli.py", line 1122, in erasePkgs
    rms = self.remove(pattern=arg)
  File "/usr/lib/python2.7/site-packages/yum/__init__.py", line 5121, in remove
    return self._at_groupremove(kwargs['pattern'])
  File "/usr/lib/python2.7/site-packages/yum/__init__.py", line 4338, in _at_groupremove
    txmbrs = self.groupRemove(group_string)
  File "/usr/lib/python2.7/site-packages/yum/__init__.py", line 3525, in groupRemove
    igroup_data = self._groupInstalledData(thisgroup)
  File "/usr/lib/python2.7/site-packages/yum/__init__.py", line 3307, in _groupInstalledData
    if group.groupid in self.igroups.groups:
AttributeError: 'InstalledGroup' object has no attribute 'groupid'


Additional info:
yum-3.4.3-54.fc18 works correctly