Simplify pip options/constraints mechanism

The current constraints generation for the
installation involves multiple tasks and multiple
variables.

Using multiple tasks extends the installation time
unnecessarily and the additional variables are
unnecessary.

This patch aims to simplify the mechanism and
hopes to speed it up a little.

Change-Id: I6784878e7a46560bebfb0be9d51b048da3774f70

defaults/main.yml

@@ -29,8 +29,6 @@ zaqar_venv_localpath: /opt/kong/zaqar.tgz
 
 zaqar_git_repo: https://github.com/openstack/zaqar
 zaqar_git_install_branch: master
-zaqar_requirements_git_repo: https://git.openstack.org/openstack/requirements
-zaqar_requirements_git_install_branch: master
 zaqar_developer_mode: false
 zaqar_developer_constraints:
   - "git+{{ zaqar_git_repo }}@{{ zaqar_git_install_branch }}#egg=zaqar"

tasks/zaqar_install.yml

@@ -33,37 +33,13 @@
     - zaqar-install
     - zaqar-pip-packages
 
-- name: Clone requirements git repository
-  git:
-    repo: "{{ zaqar_requirements_git_repo }}"
-    dest: "/opt/requirements"
-    clone: yes
-    update: yes
-    version: "{{ zaqar_requirements_git_install_branch }}"
-  when:
-    - zaqar_developer_mode | bool
-    - not zaqar_local_mode | bool
-  tags:
-    - zaqar-install
-    - zaqar-pip-packages
-
-- name: Add constraints to pip_install_options fact for developer mode
-  set_fact:
-    pip_install_options: "{{ pip_install_options|default('') }} --constraint /opt/developer-pip-constraints.txt --constraint /opt/requirements/upper-constraints.txt"
-  when:
-    - zaqar_developer_mode | bool
-    - "'/opt/developer-pip-constraints.txt' not in pip_install_options|default('')"
-    - "'/opt/requirements/upper-constraints.txt' not in pip_install_options|default('')"
-    - not zaqar_local_mode | bool
-  tags:
-    - zaqar-install
-    - zaqar-pip-packages
-
 - name: Install requires pip packages
   pip:
     name: "{{ zaqar_requires_pip_packages | join(' ') }}"
     state: latest
-    extra_args: "{{ pip_install_options|default('') }}"
+    extra_args: >-
+      {{ (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
@@ -174,7 +150,10 @@
     state: latest
     virtualenv: "{{ zaqar_bin | dirname }}"
     virtualenv_site_packages: "no"
-    extra_args: "{{ pip_install_options|default('') }}"
+    extra_args: >-
+      {{ zaqar_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