Description of problem:
The latest thunderbird-lightning update is failing to install because it requires thunderbird >= 5.0 which doesn't exist for Fedora 15.

$ sudo yum -y update
Loaded plugins: downloadonly, fastestmirror, langpacks, presto, refresh-
              : packagekit
Loading mirror speeds from cached hostfile
 * fedora: dl.fedoraproject.org
 * updates: dl.fedoraproject.org
Setting up Update Process
Resolving Dependencies
--> Running transaction check
---> Package thunderbird-lightning.x86_64 0:1.0-0.41.b3pre.fc15 will be updated
---> Package thunderbird-lightning.x86_64 0:1.0-0.44.b3pre.fc15 will be an update
--> Processing Dependency: thunderbird >= 5.0 for package: thunderbird-lightning-1.0-0.44.b3pre.fc15.x86_64
--> Finished Dependency Resolution
Error: Package: thunderbird-lightning-1.0-0.44.b3pre.fc15.x86_64 (updates)
           Requires: thunderbird >= 5.0
           Installed: thunderbird-3.1.11-1.fc15.x86_64 (@updates)
               thunderbird = 3.1.11-1.fc15
           Available: thunderbird-3.1.10-1.fc15.x86_64 (fedora)
               thunderbird = 3.1.10-1.fc15
 You could try using --skip-broken to work around the problem
 You could try running: rpm -Va --nofiles --nodigest



Version-Release number of selected component (if applicable):
thunderbird-lightning.x86_64 0:1.0-0.44.b3pre.fc15

How reproducible:
every time

Steps to Reproduce:
1. yum -y update
  
Actual results:
thunderbird-lightning-1.0-0.44.b3pre.fc15 fails to install and breaks yum update for other packages

Expected results:
yum update succeeds

Additional info:
'yum --skip-broken -y update' allows me to skip over thunderbird-lightning