Shit happens — Be on top of it.
Create the app in the region you want
$ heroku create --region <region> y-sentry
Then set the proper buildpack
$ heroku config:set BUILDPACK_URL=https://github.com/ddollar/heroku-buildpack-multi.git
$ git push heroku master
$ heroku config:set SENTRY_URL_PREFIX="https://y-sentry.herokuapp.com"
$ heroku config:set SENTRY_KEY="a-great-unique-secret-string"
$ heroku config:set SENTRY_CONF="sentry.conf.py"
$ heroku addons:add newrelic
$ heroku addons:add mandrill
$ heroku addons:add rediscloud
$ heroku addons:add heroku-postgresql:hobby-dev
$ heroku run sentry upgrade
$ heroku run sentry createsuperuser
$ heroku run sentry repair --owner=<username>