Description of problem:
I was installing a program (can't remember which), and after dnf had downloaded the package it crashed with this error. Not sure how to reproduce, I haven't come across it since.

Version-Release number of selected component:
dnf-0.4.8-1.fc20

Additional info:
reporter:       libreport-2.1.9
cmdline:        /usr/bin/python /bin/dnf install vlc
executable:     /bin/dnf
kernel:         3.11.9-300.fc20.x86_64
runlevel:       N 5
type:           Python
uid:            0

Truncated backtrace:
base.py:2159:_retrievePublicKey:ValueError: I/O operation on closed file

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 192, in _main
    return_code, resultmsgs = base.do_transaction()
  File "/usr/lib/python2.7/site-packages/dnf/cli/cli.py", line 198, in do_transaction
    if self.gpgsigcheck(downloadpkgs) != 0:
  File "/usr/lib/python2.7/site-packages/dnf/cli/cli.py", line 233, in gpgsigcheck
    self.getKeyForPackage(po, fn)
  File "/usr/lib/python2.7/site-packages/dnf/base.py", line 2263, in getKeyForPackage
    keys = self._retrievePublicKey(keyurl, repo)
  File "/usr/lib/python2.7/site-packages/dnf/base.py", line 2159, in _retrievePublicKey
    rawkey = dnf.util.urlopen(keyurl, repo).read()
ValueError: I/O operation on closed file

Local variables in innermost frame:
self: <dnf.cli.cli.BaseCli object at 0x7f1bc1a42bd0>
key_installed: False
keyurl: 'file:///etc/pki/rpm-gpg/RPM-GPG-KEY-rpmfusion-free-fedora-latest'
repo: <Repo rpmfusion-free-rawhide>
msg: u'Retrieving key from file:///etc/pki/rpm-gpg/RPM-GPG-KEY-rpmfusion-free-fedora-latest'
getSig: True