Remove unnecessary overrides of ansible_python_interpreter

Bifrost cannot operate in virtual environments without system site
packages, so overriding ansible_python_interpreter to system Python
is not necessary.

Document this limitations.

Change-Id: I669c4e248d23f65015533635ed09dcaf60f8f8f2

bifrost/cli.py

@@ -26,7 +26,6 @@ COMMON_ENV = {
     'VENV': VENV,
 }
 COMMON_PARAMS = [
-    '-e', 'ansible_python_interpreter=%s/bin/python3' % VENV,
     '-e', 'bifrost_venv_dir=%s' % VENV,
 ]
 BASE = os.path.abspath(os.path.join(os.path.dirname(sys.argv[0]), '..'))

doc/source/install/index.rst

@@ -279,6 +279,10 @@ before calling ``env-setup.sh``::
 If you're using the ansible playbooks directly (without the helper scripts),
 set the ``bifrost_venv_dir`` variables accordingly.
 
+.. note::
+   Because of Ansible dependencies Bifrost only supports virtual environments
+   created with ``--system-site-packages``.
+
 Pre-installation settings
 =========================
 

playbooks/roles/bifrost-create-vm-nodes/tasks/main.yml

@@ -12,16 +12,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 ---
-# NOTE(hwoarang) The 'apt' module needs python-apt installed in the virtualenv
-# but it's not possible to do that. See https://github.com/ansible/ansible/issues/14468
-# python-apt only works if it's installed on the local system so we need to switch the
-# Ansible python interpreter.
 - name: "Update apt cache if Ubuntu/Debian"
   apt:
     update_cache: yes
   when: ansible_os_family == "Debian"
-  vars:
-    ansible_python_interpreter: '/usr/bin/python3'
 
 - name: "Load distribution defaults"
   include_vars: "{{ item }}"
@@ -36,16 +30,10 @@
     - "../defaults/required_defaults_{{ ansible_distribution }}_{{ ansible_distribution_version }}.yml"
     - "../defaults/dummy-defaults.yml"
 
-# NOTE(hwoarang) The 'apt' module needs python-apt installed in the virtualenv
-# but it's not possible to do that. See https://github.com/ansible/ansible/issues/14468
-# python-apt only works if it's installed on the local system so we need to switch the
-# Ansible python interpreter.
 - name: "Install required packages"
   package:
     name: "{{ required_packages }}"
     state: present
-  vars:
-    ansible_python_interpreter: '/usr/bin/python3'
 
 - name: ensure installation root folder exists
   become: yes

releasenotes/notes/interpreter-a6cd3a98e9cd239f.yaml

@@ -0,0 +1,5 @@
+---
+issues:
+  - |
+    Because of Ansible dependencies Bifrost only works on virtual environments
+    created with ``--system-site-packages``.

scripts/test-bifrost.sh

@@ -163,7 +163,6 @@ export BIFROST_INVENTORY_SOURCE=${BAREMETAL_DATA_FILE}
 ${ANSIBLE} -vvvv \
     -i inventory/bifrost_inventory.py \
     ${TEST_PLAYBOOK} \
-    -e ansible_python_interpreter="${ANSIBLE_PYTHON_INTERP}" \
     -e use_cirros=${USE_CIRROS} \
     -e testing_user=${TESTING_USER} \
     -e test_vm_num_nodes=${TEST_VM_NUM_NODES} \