Use constraints for all pip package installations

Currently we're installing pip packages into the venv
unconstrained, resulting in the possibility of an
inconsistent build. This has luckily been covered by
the repo build process only making a single, correct
version of a python package available. However, for
role tests it is now failing because it's pulling in
a new version of libvirt-python which doesn't work
with the libvirt version used in newton.

Change-Id: I1607685ac6b30b698dacf5f05c4f5639ae53df44

tasks/nova_compute_kvm_install.yml

@@ -51,7 +51,10 @@
     state: latest
     virtualenv: "{{ nova_bin | dirname }}"
     virtualenv_site_packages: "no"
-    extra_args: "{{ pip_install_options|default('') }}"
+    extra_args: >-
+      {{ nova_developer_mode | ternary('--constraint /opt/developer-pip-constraints.txt', '') }}
+      {{ (pip_install_upper_constraints is defined) | ternary('--constraint ' + pip_install_upper_constraints | default(''),'') }}
+      {{ pip_install_options | default('') }}
   register: install_packages
   until: install_packages|success
   retries: 5

tasks/nova_compute_powervm_install.yml

@@ -108,7 +108,10 @@
     state: latest
     virtualenv: "{{ nova_bin | dirname }}"
     virtualenv_site_packages: "no"
-    extra_args: "{{ pip_install_options|default('') }}"
+    extra_args: >-
+      {{ nova_developer_mode | ternary('--constraint /opt/developer-pip-constraints.txt', '') }}
+      {{ (pip_install_upper_constraints is defined) | ternary('--constraint ' + pip_install_upper_constraints | default(''),'') }}
+      {{ pip_install_options | default('') }}
   register: install_packages
   until: install_packages|success
   retries: 5

tasks/nova_console_novnc_install.yml

@@ -62,7 +62,10 @@
     state: latest
     virtualenv: "{{ nova_bin | dirname }}"
     virtualenv_site_packages: "no"
-    extra_args: "{{ pip_install_options|default('') }}"
+    extra_args: >-
+      {{ nova_developer_mode | ternary('--constraint /opt/developer-pip-constraints.txt', '') }}
+      {{ (pip_install_upper_constraints is defined) | ternary('--constraint ' + pip_install_upper_constraints | default(''),'') }}
+      {{ pip_install_options | default('') }}
   register: install_packages
   until: install_packages|success
   retries: 5