Description of problem:
On el6, the mock RPM has a missing dependency: python-argparse

Version-Release number of selected component (if applicable):
mock-1.3.3-1.el6.noarch

How reproducible:
Easily reproducible

Steps to Reproduce:
1. On a fresh centos6
2. yum install mock
3.  `/usr/bin/mock` fails with `ImportError: No module named argparse`
4. yum install python-argparse
5. `/usr/bin/mock` is working correctly.

Actual results:

[root@localhost packages-t-functional]# yum install mock
Loaded plugins: fastestmirror
Setting up Install Process
Loading mirror speeds from cached hostfile
Resolving Dependencies
--> Running transaction check
---> Package mock.noarch 0:1.3.3-1.el6 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

======================================================================================================================================
 Package                      Arch                           Version                               Repository                    Size
======================================================================================================================================
Installing:
 mock                         noarch                         1.3.3-1.el6                           epel                         171 k

Transaction Summary
======================================================================================================================================
Install       1 Package(s)

Total download size: 171 k
Installed size: 533 k
Is this ok [y/N]: y
Downloading Packages:
mock-1.3.3-1.el6.noarch.rpm                                                                                    | 171 kB     00:00
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing : mock-1.3.3-1.el6.noarch                                                                                            1/1
  Verifying  : mock-1.3.3-1.el6.noarch                                                                                            1/1

Installed:
  mock.noarch 0:1.3.3-1.el6

Complete!
[root@localhost packages-t-functional]# /usr/bin/mock
Traceback (most recent call last):
  File "/usr/libexec/mock/mock", line 80, in <module>
    from mockbuild.buildroot import Buildroot
  File "/usr/lib/python2.6/site-packages/mockbuild/buildroot.py", line 20, in <module>
    from .package_manager import package_manager
  File "/usr/lib/python2.6/site-packages/mockbuild/package_manager.py", line 9, in <module>
    import distro
  File "/usr/lib/python2.6/site-packages/distro.py", line 37, in <module>
    import argparse
ImportError: No module named argparse


Expected results:

[root@localhost packages-t-functional]# /usr/bin/mock
INFO: mock.py version 1.3.3 starting (python version = 2.6.6)...
Start: init plugins
INFO: selinux disabled
Finish: init plugins
Start: run
CRITICAL: No package specified to rebuild command.



Additional info:

RPM python-argparse is needed.