Ensure that the rally venv build is self contained

Rally ships it's own version of upper-constraints [1].

As we move openstack-ansible to using the new pip resolver this
causes several issues. The rally specific version of u-c contains
constraints for pip/setuptools/wheel which will inevitably be in
conflict with those in global-requirement-pins. This results in
several problems.

* Rally is branchless and so applying branch-specific versions
  of openstack u-c is incorrect

* Rally should be installed using the rally u-c rather than
  openstack u-c

* Rally should not use the repo server to build wheels as the repo
  server wheel build venv will have different versions of pip/
  setuptools/wheel to those specificed in rally u-c.

* Rally venv build should not be subject to openstack-ansible
  global-requirement-pins as these are in conflict with rally u-c.

This patch introduces the changes necessary to build rally in a self
contained manner on the utility host with no use of the repo server.
It also includes a revert of I73887784cbc3ce6089a42c67871dbc6c3d54acf6.

[1] https://opendev.org/openstack/rally-openstack/raw/branch/master/upper-constraints.txt

Change-Id: Idbd71ade1ab82d2d218e560b2f10c38116ff47e3

defaults/main.yml

@@ -46,7 +46,7 @@ rally_database_connection_string: mysql+pymysql://{{ rally_galera_user }}:{{ ral
 # NOTE(mnaser): This uses the Rally upper-constraints because it
 #               is branchless and maintains it's own constraints,
 #               outside of requirements.
-rally_upper_constraints_url: "https://releases.openstack.org/constraints/upper/master"
+rally_upper_constraints_url: "https://opendev.org/openstack/rally-openstack/raw/branch/master/upper-constraints.txt"
 rally_git_constraints:
   - "--constraint {{ rally_upper_constraints_url }}"
 rally_pip_packages:

tasks/main.yml

@@ -51,10 +51,13 @@
   vars:
     venv_python_executable: "{{ rally_venv_python_executable }}"
     venv_build_constraints: "{{ rally_git_constraints }}"
+    venv_build_global_constraints: "{{ [] }}"
+    venv_build_distro_package_list: "{{ rally_devel_distro_packages }}"
     venv_install_destination_path: "{{ rally_bin | dirname }}"
     venv_install_distro_package_list: "{{ rally_distro_packages }}"
     venv_pip_install_args: "{{ rally_pip_install_args }}"
     venv_pip_packages: "{{ rally_pip_packages }}"
+    venv_wheel_build_enable: false
     venv_facts_when_changed:
       - section: "rally"
         option: "venv_tag"

vars/debian.yml

@@ -15,4 +15,7 @@
 
 cache_timeout: 600
 
+rally_devel_distro_packages:
+  - libpython3-dev
+
 rally_distro_packages: []

vars/redhat.yml

@@ -13,4 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+rally_devel_distro_packages:
+  - python36-devel
+
 rally_distro_packages: []