Using get text in gem and code

I recently converted a large Rails 3 application into a gem.
Localization
is part of the original code base.

I modified the gettext:find task to look in the gem and in any app
that
uses the gem to find potential translations.

namespace :gettext do
def files_to_translate
files_in_application + files_in_gem
end

def files_in_application
Dir.glob(glob_pattern)
end

def files_in_gem
Dir.glob(File.join(MyGem.root, glob_pattern))
end

def glob_pattern
“{app,lib,config,locale}/**/*.{rb,erb,haml,slim,rhtml}”
end
end

Hence, the task looks in the gem root and, as before, Rails.root for
files to translate.

My question: Is there a way to find .po files in both places? I am OK
with .mo files being stored in Rails.root/locales. (The .mo files can
then be checked into the repo for the app without affecting the gem
repo.)
But I would like a way for the .po files of the gem to override any
.po
files in the app.

Any ideas?

Martin