Enforce using pymysql as mysql dialect when creating mysql containers.

Author: shunping

sdks/python/apache_beam/io/external/xlang_jdbcio_it_test.py

@@ -121,7 +121,7 @@ class CrossLanguageJdbcIOTest(unittest.TestCase):
           'postgresql',
           'org.postgresql.Driver'),
       'mysql': DbData(
-          lambda: MySqlContainer(), ['mysql:mysql-connector-java:8.0.28'],
+          lambda: MySqlContainer(dialect='pymysql'), ['mysql:mysql-connector-java:8.0.28'],
           'mysql',
           'com.mysql.cj.jdbc.Driver')
   }

sdks/python/apache_beam/yaml/integration_tests.py

@@ -228,7 +228,7 @@ def temp_mysql_database():
                              with the MySQL database during setup.
       Exception: Any other exception encountered during the setup process.
   """
-  with MySqlContainer(init=True) as mysql_container:
+  with MySqlContainer(init=True, dialect='pymysql') as mysql_container:
     try:
       # Make connection to temp database and create tmp table
       engine = sqlalchemy.create_engine(mysql_container.get_connection_url())