Since 066b8d8f75b8, the push command accept multiple destination. infinitepush
was not aware of that. We now use the new urlutil.get_push_paths function to
determine the push destination, fixing the issue. This will also make future
evolution of that logic transparent for infinitepush
We still disallow push to multiple destinations if infinite push is enabled
because I don't know what this means for infinite push. However user will now
get a clear error message instead of a crash.