Description of problem:
I tried to install simple package in minimal virtual machine and dnf finish with nice python traceback.


Version-Release number of selected component (if applicable):
[root@vm-058 ~]# rpm -q dnf libsolv
dnf-0.4.20-1.fc20.noarch
libsolv-0.6.0-0.git05baf54.fc20.x86_64

[root@vm-058 ~]# rpm -qa | wc -l
313


How reproducible:
Always

Steps to Reproduce:
1. install minimal vm. (you can use fedora docker image)
2. yum install -y dnf
3. remove cache "rm -f /var/cache/dnf/" #this step is optional
4. dnf makecache
5. dnf install dstat

Actual results:
[root@vm-058 ~]# dnf install dstat
Resolving dependencies
--> Starting dependency resolution
---> Package dstat.noarch 0.7.2-12.fc20 will be installed
--> Finished dependency resolution
Dependencies resolved.

================================================================================================================================
 Package                    Arch                        Version                               Repository                   Size
================================================================================================================================
Installing:
 dstat                      noarch                      0.7.2-12.fc20                         fedora                        0  

Transaction Summary
================================================================================================================================
Install  1 Package

Installed size: 0  
Downloading Packages:
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 242, in user_main
    errcode = main(args)
  File "/usr/lib/python2.7/site-packages/dnf/cli/main.py", line 75, in main
    return _main(base, args)
  File "/usr/lib/python2.7/site-packages/dnf/cli/main.py", line 156, in _main
    return_code, resultmsgs = base.do_transaction()
  File "/usr/lib/python2.7/site-packages/dnf/cli/cli.py", line 214, in do_transaction
    self.download_packages(downloadpkgs, self.output.progress, total_cb)
  File "/usr/lib/python2.7/site-packages/dnf/base.py", line 909, in download_packages
    errors = dnf.repo.download_payloads(payloads, drpm)
  File "/usr/lib/python2.7/site-packages/dnf/repo.py", line 97, in download_payloads
    targets = [pload.librepo_target() for pload in payloads]
  File "/usr/lib/python2.7/site-packages/dnf/repo.py", line 278, in librepo_target
    target_dct.update(self._target_params())
  File "/usr/lib/python2.7/site-packages/dnf/repo.py", line 289, in _target_params
    ctype, csum = pkg.returnIdSum()
  File "/usr/lib/python2.7/site-packages/dnf/package.py", line 174, in returnIdSum
    (chksum_type, chksum) = self.chksum
  File "/usr/lib/python2.7/site-packages/dnf/package.py", line 52, in chksum
    return super(Package, self).chksum
AttributeError: No such checksum.

Expected results:
Pacakge dstat should be installed

[root@vm-058 ~]# yum install -y dstat
Resolving Dependencies
--> Running transaction check
---> Package dstat.noarch 0:0.7.2-12.fc20 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================
 Package        Arch            Version                   Repository       Size
================================================================================
Installing:
 dstat          noarch          0.7.2-12.fc20             fedora          163 k

Transaction Summary
================================================================================
Install  1 Package

Total download size: 163 k
Installed size: 752 k
Downloading packages:
dstat-0.7.2-12.fc20.noarch.rpm                             | 163 kB   00:00     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : dstat-0.7.2-12.fc20.noarch                                   1/1 
  Verifying  : dstat-0.7.2-12.fc20.noarch                                   1/1 

Installed:
  dstat.noarch 0:0.7.2-12.fc20                                                  

Complete!