Created attachment 931661 [details]
debugdata.tar

Description of problem:
dnf group install "Development Tools" fails with a traceback.

Version-Release number of selected component (if applicable):
dnf-0.6.0-1.fc21.noarch
hawkey-0.5.0-2.fc21.x86_64

How reproducible:
Always

Steps to Reproduce:
1. dnf group install "Development Tools"

Actual results:

# dnf group install "Development Tools"
Dependencies resolved.
Traceback (most recent call last):
  File "/usr/bin/dnf", line 36, in <module>
    main.user_main(sys.argv[1:], exit_code=True)
  File "/usr/lib/python2.7/site-packages/dnf/cli/main.py", line 182, in user_main
    errcode = main(args)
  File "/usr/lib/python2.7/site-packages/dnf/cli/main.py", line 84, in main
    return _main(base, args)
  File "/usr/lib/python2.7/site-packages/dnf/cli/main.py", line 141, in _main
    ret = resolving(cli, base)
  File "/usr/lib/python2.7/site-packages/dnf/cli/main.py", line 160, in resolving
    base.do_transaction()
  File "/usr/lib/python2.7/site-packages/dnf/cli/cli.py", line 185, in do_transaction
    grp_diff = self._groups_diff()
  File "/usr/lib/python2.7/site-packages/dnf/cli/cli.py", line 145, in _groups_diff
    return self.group_persistor.diff()
  File "/usr/lib/python2.7/site-packages/dnf/persistor.py", line 273, in diff
    return _GroupsDiff(self._original, self.db)
  File "/usr/lib/python2.7/site-packages/dnf/persistor.py", line 170, in __init__
    self.added, self.removed = _diff_dcts(db_old, db_new)
  File "/usr/lib/python2.7/site-packages/dnf/persistor.py", line 60, in _diff_dcts
    keys1 = set(dct1.keys())
AttributeError: 'NoneType' object has no attribute 'keys'

Expected results:

To install that group.

Additional info: