packit: try a different way to get upstream version

packit.yaml

@@ -1,11 +1,11 @@
 upstream_project_url: https://github.com/candlepin/subscription-manager
 srpm_build_deps:
+  - python3
   - tito
 actions:
   pre-sync:
     - tito build -o . --tgz
-  get-current-version:
-    - git describe --tags --abbrev=0 --match='subscription-manager-*' | sed -e 's,subscription-manager-,,g;s,-[0-9]\+$,,g'
+  get-current-version: python3 setup.py --version
 specfile_path: subscription-manager.spec
 upstream_tag_template: "subscription-manager-{version}"
 jobs: