Automatically install pymysql or psycopg2 if necessary

If a user is supplying a pymysql or psycopg2 connection string, the
necessary driver needs to be installed before it can be used.

Change-Id: I4655c9a39fea6a43f7e579f099d61836577202f0

defaults/main.yml

@@ -35,6 +35,7 @@ ara:
       # Defaults to the latest version on PyPi or the master branch when installing from source
       version:
   config:
+    # If pymysql or psycopg2 are found in the connection string, the role will install the necessary driver
     database: "sqlite:////var/lib/ara/ansible.sqlite"
     # Host to listen on for embedded server, apache or nginx
     host: 127.0.0.1

tasks/install/pip.yml

@@ -55,6 +55,22 @@
     state: present
     virtualenv: "{{ ara.install.pip.virtualenv | bool | ternary(ara.install.pip.virtualenv_path, omit) }}"
 
+- name: Install pymysql with pip
+  become: true
+  pip:
+    name: pymysql
+    state: present
+    virtualenv: "{{ ara.install.pip.virtualenv | bool | ternary(ara.install.pip.virtualenv_path, omit) }}"
+  when: '"pymysql" in ara.config.database'
+
+- name: Install psycopg2 with pip
+  become: true
+  pip:
+    name: psycopg2
+    state: present
+    virtualenv: "{{ ara.install.pip.virtualenv | bool | ternary(ara.install.pip.virtualenv_path, omit) }}"
+  when: '"psycopg2" in ara.config.database'
+
 - name: Suffix the virtualenv bin directory to PATH
   set_fact:
     path_with_virtualenv: "{{ ara.install.pip.virtualenv_path }}/bin:{{ ansible_env.PATH }}"