Description of problem:
When BuildRequires: are specified as file instead of dependency name, mock fails
to install them, even though yum resolvedep has no problems.

Version-Release number of selected component (if applicable):
$ rpm -q mock
mock-0.8.18-1.fc7

How reproducible:
Always

Steps to Reproduce:
1. wget http://dl.atrpms.net/all/arpack-2.1-7.src.rpm
2. mock -r fedora-7-x86_64 rebuild arpack-2.1-7.src.rpm
  
Actual results:
INFO: mock.py version 0.8.18 starting...
State Changed: init plugins
State Changed: start
INFO: Start(/home/rathann/build/RPMS/arpack-2.1-7.fc7.src.rpm) 
Config(fedora-7-x86_64)
State Changed: lock buildroot
State Changed: clean
State Changed: init
State Changed: lock buildroot
INFO: enabled yum cache
State Changed: cleaning yum metadata
INFO: enabled root cache
State Changed: unpacking cache
State Changed: running yum
State Changed: setup
ERROR: Exception(/home/rathann/build/RPMS/arpack-2.1-7.fc7.src.rpm)
Config(fedora-7-x86_64) 0 minutes 28 seconds
INFO: Results and/or logs in: /var/lib/mock//fedora-7-x86_64/result
ERROR: Bad build req: No Package Found for /usr/lib64/liblapack.so. Exiting.


Expected results:
BRs should be resolved correctly.

Additional info:
$ yum resolvedep /usr/lib64/liblapack.so
Loading "fedorakmod" plugin
Loading "basearchonly" plugin
Loading "fastestmirror" plugin
Loading mirror speeds from cached hostfile
 * livna: rpm.livna.org
 * fedora: ftp.ps.pl
 * updates: ftp.wcss.pl
Importing additional filelist information
0:lapack-devel-3.1.1-1.fc7.x86_64