Handle empty PO files
Handle empty PO files

Some projects like oslo.messaging and oslo.reports have now empty PO
files. Pushing empty files to transifex results in an error.

Check before pushing of the main file whether it's empty and only
push if it's non-empty - like it's done for the log-level PO
files already.

Change-Id: Ia757e9d4b88bc8eb7b1ce800a25fe0ed1ebe3e76

Tesora/tesora-project-config,noorul/os-project-config,openstack-infra/project-config,dongwenjuan/project-config,dongwenjuan/project-config,noorul/os-project-config,openstack-infra/project-config,Tesora/tesora-project-config