Default nodepool_pip_executable to pip3

Moving forward, we'll only support nodepool under python3.

Change-Id: If0f9ed013819b68601e28ecfbeffa40a41d19ebc
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

.zuul.yaml

@@ -6,10 +6,6 @@
       - name: openstack-infra/nodepool
     roles:
       - zuul: openstack/ansible-role-nodepool
-    vars:
-      # TODO(pabelanger): This needs to fix to defaut to this when not using
-      # a virtualenv.
-      nodepool_pip_executable: pip3
 
 # Testing for nodepool_install_method: pip
 - job:

README.rst

@@ -20,6 +20,8 @@ including Jenkins and Zuul.
 Requirements
 ------------
 
+* pip3 to be installed if using nodepool_install_method: (git|pip)
+
 Packages
 ~~~~~~~~
 

tasks/install.yaml

@@ -25,4 +25,12 @@
   with_items: "{{ nodepool_build_depends }}"
   when: nodepool_install_method == 'git'
 
+- name: Define nodepool_pip_executable if needed.
+  set_fact:
+    nodepool_pip_executable: pip3
+  when:
+    - nodepool_install_method == 'git' or nodepool_install_method == 'pip'
+    - nodepool_pip_virtualenv_python is not defined
+    - nodepool_pip_executable is not defined
+
 - include: "install/{{ nodepool_install_method }}.yaml"