download-artifacts: only consider the most recent build

If the download-artifacts query returns more than one build, only
use the most recent one, as earlier builds may be for failed gate
runs and fetching them may fail.

Also, fix one more location which was missing an "artifacts/"
path prefix when returing artifacts.

Change-Id: If988d1f2bea863e0dad267359515018aae25ad45

playbooks/python/tarball-post.yaml

@@ -34,7 +34,7 @@
           zuul:
             artifacts:
               - name: "python_sdist"
-                url: "{{ item.path | basename }}"
+                url: "artifacts/{{ item.path | basename }}"
                 metadata:
                   type: python_sdist
 

roles/download-artifact/tasks/inner.yaml

@@ -1,8 +0,0 @@
-- name: Download archive
-  uri:
-    url: "{{ artifact.url }}"
-    dest: "{{ download_artifact_directory }}"
-  loop: "{{ build.artifacts }}"
-  loop_control:
-    loop_var: artifact
-  when: "artifact.name == download_artifact_name or ((download_artifact_name | type_debug) == 'list' and artifact.name in download_artifact_name)"

roles/download-artifact/tasks/main.yaml

@@ -2,8 +2,14 @@
   uri:
     url: "{{ download_artifact_api }}/builds?{{ download_artifact_query }}"
   register: build
-- name: Process build
-  loop: "{{ build.json }}"
+- name: Parse build response
+  set_fact:
+    build: "{{ build.json[-1] }}"
+- name: Download archive
+  uri:
+    url: "{{ artifact.url }}"
+    dest: "{{ download_artifact_directory }}"
+  loop: "{{ build.artifacts }}"
   loop_control:
-    loop_var: build
-  include_tasks: inner.yaml
+    loop_var: artifact
+  when: "artifact.name == download_artifact_name or ((download_artifact_name | type_debug) == 'list' and artifact.name in download_artifact_name)"