Description of problem:
system-config-language backtraces when there is a yum dependency problem.
It should just give up with a warning.

How reproducible:
every time

Steps to Reproduce:
1. install newer openoffice build from koji say
2. run system-config-language 
3. select a new language group
  
Actual results:
Loaded plugins: refresh-packagekit
Package lohit-fonts-kannada-2.2.0-1.fc9.noarch already installed and latest version
1:openoffice.org-langpack-kn_IN-2.4.0-12.6.fc9.i386 from rawhide has depsolving
problems
  --> Missing Dependency: openoffice.org-core = 1:2.4.0-12.6.fc9 is needed by
package 1:openoffice.org-langpack-kn_IN-2.4.0-12.6.fc9.i386 (rawhide)
Traceback (most recent call last):
  File "/usr/share/system-config-language/language_gui.py", line 173, in okClicked
    self.apply()
  File "/usr/share/system-config-language/language_gui.py", line 235, in apply
    install.install_language (self.mainWindow, grpid)                           
  File "/usr/share/system-config-language/gui_install.py", line 385, in
install_language
    self.checkDeps(mainWindow)
  File "/usr/share/system-config-language/gui_install.py", line 154, in checkDeps
    d.set_details(string.join(msgs, "\n"))
NameError: global name 'string' is not defined

Expected results:
no backtrace