Description of problem:
tb-lightning-gdata is not installable on top of tb-lightning:

[mrunge@turing ~]$ sudo yum install thunderbird-lightning-gdata
Loaded plugins: langpacks, refresh-packagekit
Resolving Dependencies
--> Running transaction check
---> Package thunderbird-lightning-gdata.x86_64 0:0.18-5.fc20 will be installed
--> Processing Dependency: thunderbird-lightning(x86-64) = 1.9.1-5.fc20 for package: thunderbird-lightning-gdata-0.18-5.fc20.x86_64
--> Finished Dependency Resolution
Error: Package: thunderbird-lightning-gdata-0.18-5.fc20.x86_64 (euler-releases)
           Requires: thunderbird-lightning(x86-64) = 1.9.1-5.fc20
           Installed: thunderbird-lightning-2.6-1.fc20.x86_64 (@euler-updates-testing)
               thunderbird-lightning(x86-64) = 2.6-1.fc20
           Available: thunderbird-lightning-1.9.1-5.fc20.x86_64 (euler-releases)
               thunderbird-lightning(x86-64) = 1.9.1-5.fc20
 You could try using --skip-broken to work around the problem
 You could try running: rpm -Va --nofiles --nodigest

[mrunge@turing ~]$ rpm -q thunderbird-lightning
thunderbird-lightning-2.6-1.fc20.x86_64

It looks like patches from rawhide were not merged into f20?