[minor] chore: force AWS region in Travis test script

Author: fquffio

.travis.yml

@@ -6,7 +6,7 @@ install:
   - 'pip install awscli'
 
 script:
-  - 'for template in $(ls *.yml); do aws cloudformation validate-template --template-body file://$template; done'
+  - 'for template in $(ls *.yml); do aws cloudformation validate-template --template-body file://$template --region $AWS_DEFAULT_REGION; done'
 
 before_deploy:
   - 'mkdir -p templates'