Fix tripleo-repos cross-platform installation

In order to make this role work with pure/clean images and also with
altered images like the ones provided by infra we need to detect
which virtualenv executable is available.

On clean fedora28 systems virtualenv is installed by python3-virtualend
package and provideds virtualenv-3 command.

On infra images, virtualenv is installed manually and disabled as rpm
and we do no thave an virtualenv-3 executable. Still, we can expect
to have a working virtualenv on.

On CentOS-7, there is no python-pip package, its correct name is
python2-pip.

Found the bug on another build:
http://logs.openstack.org/23/636923/20/check/tripleo-ci-molecule/c4542a5/job-output.txt.gz#_2019-03-21_19_17_35_349130

Change-Id: I7e0ee242956bcd451a2b2b6c2ab6daef978ef016
Related-Bug: https://bugs.launchpad.net/tripleo/+bug/1821575

roles/tripleo-repos/defaults/main.yml

@@ -10,18 +10,16 @@ virtualenv_python:
   yum: python
   dnf: python3
 
-python_pip:
-  yum: python-pip
-  dnf: python3-pip
-
-python_setuptools:
-  yum: python-setuptools
-  dnf: python3-setuptools
-
-python_virtualenv:
-  yum: python-virtualenv
-  dnf: python3-virtualenv
-
-python_libselinux:
-  yum: libselinux-python
-  dnf: python3-libselinux
+rpm_packages:
+  yum:
+    # we have special handling to provide pip on py27 systems
+    - git
+    - libselinux-python
+    - python-setuptools
+    - python-virtualenv
+  dnf:
+    - git
+    - python3-libselinux
+    - python3-pip
+    - python3-setuptools
+    - python3-virtualenv

roles/tripleo-repos/tasks/main.yml

@@ -2,20 +2,41 @@
 - name: install system packages
   become: true
   package:
-    name:
-      - "git"
-      - "{{ python_libselinux[ansible_pkg_mgr] }}"
-      - "{{ python_setuptools[ansible_pkg_mgr] }}"
-      - "{{ python_virtualenv[ansible_pkg_mgr] }}"
-      - "{{ python_pip[ansible_pkg_mgr] }}"
+    name: "{{ rpm_packages[ansible_pkg_mgr] }}"
     state: present
 
+- name: install pip from epel on centos-7
+  when: ansible_distribution == 'CentOS' and ansible_distribution_major_version == 7
+  block:
+    - name: install epel if needed
+      become: true
+      package:
+        name: epel-release
+
+    - name: install pip on py27 distros
+      shell: yum install -y --disableexcludes='*' /usr/bin/pip
+      register: result
+      changed_when: "'Nothing to do' not in result.stdout"
+      args:
+        warn: false
+
+# TODO(ssbarnea) workaround for https://bugs.launchpad.net/tripleo/+bug/1821575
+# virtualenv-3 is missing in infra prepared images but any version should do
+- name: detect virtualenv command to use
+  shell: command -v virtualenv-3 || command -v virtualenv
+  args:
+    warn: false
+  changed_when: false
+  register: venv_cmd
+
 - name: pip install tripleo-repos
   become: true
   pip:
     name: "{{ tripleo_repos_repository }}"
     virtualenv: "{{ workspace }}/venv"
     virtualenv_python: "{{ virtualenv_python[ansible_pkg_mgr] }}"
+    # https://github.com/ansible/ansible/issues/52275
+    virtualenv_command: "{{ venv_cmd.stdout_lines|first }}"
     virtualenv_site_packages: true
 
 - name: Set branch for building containers check jobs