Make sure bindep is on the node

OpenStack nodes pre-install bindep, but other nodes may not. Check to
see if bindep is on the node. If so, use it. If not, make a temp dir
that we remove at the end of the role and install bindep into a virtualenv
in that tempdir.

Change-Id: I3f34c178254add2143dc7f1b9758844480d7d914

roles/bindep/defaults/main.yaml

@@ -1,2 +1,4 @@
 ---
 zuul_work_dir: "src/{{ zuul.project.canonical_name }}"
+bindep_command: /usr/bindep-env/bin/bindep
+bindep_file: ""

roles/bindep/handlers/main.yaml

@@ -0,0 +1,4 @@
+- name: remove bindep temp dir
+  file:
+    path: "{{ bindep_temp_dir }}"
+    state: absent

roles/bindep/tasks/install.yaml

@@ -0,0 +1,15 @@
+- name: create temp dir for bindep
+  tempfile:
+    state: directory
+    prefix: bindep
+  register: bindep_temp_dir
+  notify:
+  - remove bindep temp dir
+
+- name: install bindep into temporary venv
+  pip:
+    name: bindep
+    virtualenv: "{{ bindep_temp_dir }}/venv"
+
+- set_fact:
+    bindep_found_command: "{{ bindep_temp_dir }}/venv/bin/bindep"

roles/bindep/tasks/main.yaml

@@ -1,12 +1,24 @@
 ---
+- stat:
+    path: "{{ bindep_command }}"
+  register: bindep_command_stat
+  failed_when: false
+
+- set_fact:
+    bindep_found_command: "{{ bindep_command }}"
+  when: bindep_command_stat is defined
+
+- include: install.yaml
+  when: bindep_command_stat is not defined
+
 - name: Install distro packages from bindep
   args:
     chdir: "{{ zuul_work_dir }}"
     executable: /bin/bash
+  environment:
+    BINDEP: "{{ bindep_command }}"
+    PACKAGES: "{{ bindep_file }}"
   shell: |
-    # set a default path to the preinstalled bindep entrypoint
-    export BINDEP=${BINDEP:-/usr/bindep-env/bin/bindep}
-
     function is_fedora {
         [ -f /usr/bin/yum ] && cat /etc/*release | grep -q -e "Fedora"
     }