added logic for conflict between pg user and drupal pg admin

tasks/main.yml

diff --git a/tasks/main.yml b/tasks/main.yml
index 434cce6..24af9d9 100644
--- a/tasks/main.yml
+++ b/tasks/main.yml
@@ -1,5 +1,10 @@
 ---
 # tasks file for apigee-opdk-devportal-config
+- name: Drupal Admin and Postgres admin cannot be the same username
+  fail:
+    msg: "Drupal admin and postgres admin cannot be the same user"
+  when: (drupal_pg_user == pg_user) or (drupal_pg_user == devportal_pg_user)
+
 - name: Construct name of dev portal response file
   cache:
     key: 'opdk_portal_config_file'