Add toggle for python wheel build process

If a package (like stackviz) should be installed using
a tarball, rather than from a git source, then it is
better to be able to disable the wheel build process,
constraints usage, etc and just install it from the
tarball.

Change-Id: Id1dc504586a3a1bbd7a161b7367606ced3789043

defaults/main.yml

@@ -95,6 +95,12 @@ venv_python_executable: "python2"
 # installed packages.
 venv_rebuild: no
 
+# Enable/disable the build of python wheels
+# If the package concerned is built from a tarball, rather
+# than from a git source or pypi, then this may be best to
+# set to false.
+venv_wheel_build_enable: "{{ venv_build_host != inventory_hostname }}"
+
 # Set the host where the wheels will be built.
 # If this host is not the same as the target host, then
 # python wheels will be built in order to speed up the

tasks/python_venv_install.yml

@@ -20,7 +20,7 @@
 
 - name: Install distro packages for venv build
   package:
-    name: "{{ (venv_build_host != inventory_hostname) | ternary(venv_install_distro_package_list, (venv_build_base_distro_package_list + venv_build_distro_package_list + venv_install_distro_package_list) | unique) }}"
+    name: "{{ (venv_wheel_build_enable | bool) | ternary(venv_install_distro_package_list, (venv_build_base_distro_package_list + venv_build_distro_package_list + venv_install_distro_package_list) | unique) }}"
     state: "{{ venv_distro_package_state }}"
     update_cache: "{{ (ansible_pkg_mgr in ['apt', 'zypper']) | ternary('yes', omit) }}"
     cache_valid_time: "{{ (ansible_pkg_mgr == 'apt') | ternary(venv_distro_cache_valid_time, omit) }}"
@@ -77,7 +77,7 @@
   copy:
     dest: "{{ venv_install_destination_path }}/constraints.txt"
     content: |
-      {% if (venv_build_host != inventory_hostname) and
+      {% if (venv_wheel_build_enable | bool) and
             (_constraints_file_slurp is defined) and
             (_constraints_file_slurp.content is defined) %}
       {{ _constraints_file_slurp.content | b64decode }}

tasks/python_venv_wheel_build.yml

@@ -17,7 +17,7 @@
   delegate_to: "{{ venv_build_host }}"
   become: "{{ venv_build_host == 'localhost' }}"
   when:
-    - venv_build_host != inventory_hostname
+    - venv_wheel_build_enable | bool
   block:
     - name: Install distro packages for wheel build
       package: