Description of problem:
Dnf search can cause traceback while running under su - USER. This is probably related to the systemd-logind bug, but dnf shouldn't behave this way. In case it is not possible to workaround this problem, dnf should exit with proper error message.

Version-Release number of selected component (if applicable):
dnf-0.4.8-1.fc20.noarch

How reproducible:
Always

Steps to Reproduce:
1. ssh to the box as root
2. su - USER (regular user)
3. dnf search '*dsd*'

Actual results:
Traceback (most recent call last):
  File "/bin/dnf", line 35, in <module>
    main.user_main(sys.argv[1:], exit_code=True)
  File "/usr/lib/python2.7/site-packages/dnf/cli/main.py", line 279, in user_main
    errcode = main(args)
  File "/usr/lib/python2.7/site-packages/dnf/cli/main.py", line 64, in main
    return _main(base, args)
  File "/usr/lib/python2.7/site-packages/dnf/cli/main.py", line 135, in _main
    result, resultmsgs = cli.run()
  File "/usr/lib/python2.7/site-packages/dnf/cli/cli.py", line 1404, in run
    load_available_repos=lar)
  File "/usr/lib/python2.7/site-packages/dnf/base.py", line 207, in fill_sack
    with dnf.lock.metadata_cache_lock:
  File "/usr/lib/python2.7/site-packages/dnf/lock.py", line 71, in __enter__
    pid = self._read_lock()
  File "/usr/lib/python2.7/site-packages/dnf/lock.py", line 40, in _read_lock
    with open(self._target, 'r') as f:
  File "/usr/lib/python2.7/site-packages/dnf/util.py", line 110, in cached_getter
    val = fn(obj)
  File "/usr/lib/python2.7/site-packages/dnf/lock.py", line 50, in _target
    dnf.util.ensure_dir(user_run_dir)
  File "/usr/lib/python2.7/site-packages/dnf/util.py", line 49, in ensure_dir
    os.makedirs(dname, mode=0o755)
  File "/usr/lib/python2.7/os.py", line 150, in makedirs
    makedirs(head, mode)
  File "/usr/lib/python2.7/os.py", line 157, in makedirs
    mkdir(name, mode)
OSError: [Errno 13] Permission denied: '/run/user/1001'

Expected results:
No traceback, dnf search results or appropriate error message.

Additional info: