Replace virtualenv with exacutable for pip

We create virtualenv with a separate command since we need to create
constraints before running pip. In the meanwhile when using pyenv
it becomes more messy to use virtualenv, as it would require
setting virtualenv_command and you can't define virtualenv_python then.

Using exacutable requires setuptools to be present
for ansible_python_interpreter

Change-Id: I5bf617ad0eca3dd5e58e25af7b44d536dc4579d3

tasks/python_venv_install.yml

@@ -55,7 +55,7 @@
 
 - name: Create the virtualenv (if it does not exist)
   command: >-
-    {{ venv_python_executable }} 
+    {{ venv_python_executable }}
     -m venv
     {{ venv_install_destination_path }}
   args:
@@ -129,7 +129,7 @@
       - setuptools
       - wheel
     state: "{{ venv_pip_package_state }}"
-    virtualenv: "{{ venv_install_destination_path }}"
+    executable: "{{ venv_install_destination_path }}/bin/pip"
     extra_args: >-
       --constraint {{ venv_install_destination_path }}/global-constraints.txt
       --constraint {{ venv_install_destination_path }}/constraints.txt
@@ -151,7 +151,7 @@
       pip:
         name: "{{ _venv_install_pip_packages }}"
         state: "{{ venv_pip_package_state }}"
-        virtualenv: "{{ venv_install_destination_path }}"
+        executable: "{{ venv_install_destination_path }}/bin/pip"
         extra_args: >-
           --constraint {{ venv_install_destination_path }}/global-constraints.txt
           --constraint {{ venv_install_destination_path }}/constraints.txt

tasks/python_venv_wheel_build.yml

@@ -105,7 +105,7 @@
           - setuptools
           - wheel
         state: "{{ venv_pip_package_state }}"
-        virtualenv: "{{ venv_build_host_venv_path }}"
+        executable: "{{ venv_build_host_venv_path }}/bin/pip"
         extra_args: >-
           --constraint {{ _venv_build_requirements_prefix }}-global-constraints.txt
           --constraint {{ _venv_build_requirements_prefix }}-source-constraints.txt

vars/main.yml

@@ -20,6 +20,7 @@ _venv_build_base_distro_package_list:
     - "{{ (venv_python_executable == 'python2') | ternary('pkg-config', 'python3-pkgconfig') }}"
     - "{{ (venv_python_executable == 'python2') | ternary('python-dev', 'python3-dev') }}"
     - python3-venv
+    - python3-setuptools
   redhat:
     - autoconf
     - cmake
@@ -30,6 +31,7 @@ _venv_build_base_distro_package_list:
 _venv_install_base_distro_package_list:
   debian:
     - python3-venv
+    - python3-setuptools
   redhat: []
 
 # Set the available build targets for all nodes within an environment.