DOCKER - Small inline bash function with inline python script to wait for database to be ready

entrypoint.sh

function postgres_ready(){
python << END
import sys
import psycopg2
try:
    conn = psycopg2.connect(dbname="$DB_NAME", user="$DB_USER", password="$DB_PASS", host="$DB_HOST")
except psycopg2.OperationalError:
    sys.exit(-1)
sys.exit(0)
END
}