python3Packages.pbr: add setuptools dependency

pbr doesn't list any explicit requirements, but it actually requires
setuptools (for pkg_resources).
Ref:
* https://bugs.launchpad.net/pbr/+bug/1868899
* https://opendev.org/openstack/pbr/src/tag/5.6.0/pbr/version.py#L439

(cherry picked from commit 21d70a8301)

pkgs/development/python-modules/pbr/default.nix

@@ -1,4 +1,4 @@
-{ lib, buildPythonPackage, fetchPypi }:
+{ lib, buildPythonPackage, fetchPypi, setuptools }:
 
 buildPythonPackage rec {
   pname = "pbr";
@@ -9,8 +9,11 @@ buildPythonPackage rec {
     sha256 = "42df03e7797b796625b1029c0400279c7c34fd7df24a7d7818a1abb5b38710dd";
   };
 
+  propagatedBuildInputs = [ setuptools ];
+
   # circular dependencies with fixtures
   doCheck = false;
+  pythonImportsCheck = [ "pbr" ];
 
   meta = with lib; {
     homepage = "http://docs.openstack.org/developer/pbr/";