Allow depending on changes we dont actually build

It is common practice in TripleO to depend on a documentation
change when changing some aspect of CI or dev tooling. However, we
can not actually build a package from these changes, so the job
will fail.

This change makes sure we only try to build the package if it maps
to some package in rdoinfo.  A debug message will be printed if no
package is found.

Change-Id: I076d1ed89bc8707630841cbcb2683295e935a944
Closes-Bug: 1679650
Co-Authored-By: Alex Schultz <aschultz@redhat.com>

roles/build-test-packages/tasks/dlrn-build.yml

@@ -38,12 +38,17 @@
     rdopkg findpkg -s $PROJECT_NAME -l rdoinfo | grep ^name | awk '{print $2}'
   args:
       chdir: '{{ build_repo_dir }}/DLRN'
-  failed_when: project_name_mapped.stdout == ''
 
-- name: Create data directory if doesn't exist yet
+- debug:
+    msg: "WARNING: Unable to build {{ artg_change.project }}. No pkg found."
+  when: project_name_mapped.stdout == ''
+
+- when: project_name_mapped.stdout != ''
+  block:
+    - name: Create data directory if doesn't exist yet
       file: path="{{ build_repo_dir }}/DLRN/data/" state=directory
 
-- name: Copy from ready directories if configured
+    - name: Copy from ready directories if configured
       command: >
         cp -raf {{ artg_repos_dir }}/{{ artg_change.project|regex_replace('openstack[^/]*/', '') }}
         {{ build_repo_dir }}/DLRN/data/{{ project_name_mapped.stdout }}
@@ -51,7 +56,7 @@
       register: copy_dir
       when: artg_repos_dir is defined
 
-- name: Clone the gated change
+    - name: Clone the gated change
       git:
         repo: '{{ artg_change.host }}/{{ artg_change.project }}'
         dest: '{{ build_repo_dir }}/DLRN/data/{{ project_name_mapped.stdout }}'
@@ -59,7 +64,7 @@
         version: 'FETCH_HEAD'
       when: artg_repos_dir is not defined or copy_dir|failed
 
-- name: Run DLRN
+    - name: Run DLRN
       shell: >
         set +e;
         source {{ build_repo_dir }}/dlrn-venv/bin/activate;
@@ -81,3 +86,4 @@
       args:
           chdir: '{{ build_repo_dir }}/DLRN'
       register: repo_built
+