Pbr is a very heavy package to depend on. It requires git-core, which is
16 MiB on my Fedora. We only use it to detect the version, which can be
done without pbr using a much lighter importlib_metadata.
Copied from https://review.opendev.org/c/openstack/osprofiler/+/739379
Change-Id: Ib10180732042bda254b058b94c9ff41f5c31c3cb