gnu: python-os-testr: Propagate python-testtools and python-babel.

Lack of python-testtools was causing the sanity-check phase to fail.

* gnu/packages/openstack.scm (python-os-testr)
[native-inputs]{python-testtools, python-babel}: Move to...
[propagated-inputs]: ... here.

gnu/packages/openstack.scm

@@ -268,9 +268,9 @@ (define-public python-os-testr
      ;; when building the package. Skip the tests for now.
      `(#:tests? #f))
     (propagated-inputs
-     (list python-subunit))
+     (list python-babel python-subunit python-testrepository python-testtools))
     (native-inputs
-     (list python-pbr python-testtools python-babel))
+     (list python-pbr))
     (home-page "https://www.openstack.org/")
     (synopsis "Testr wrapper to provide functionality for OpenStack projects")
     (description