The mysqlclient module in python3.6 is a little quirky. You don't actually import it using its package name. Try this #!/usr/bin/python3.6
print("Content-Type: text/html\n\n")
import MySQLdb
db=MySQLdb.connect(host="localhost", user="stewguy_user", passwd="password", db="stewguy_database")
Here's the documentation for it https://github.com/PyMySQL/mysqlclient-python/blob/master/doc/user_guide.rst