I am trying to access RDS Instance from AWS Glue, I have a few python scripts running in EC2 instances and I currently use PYODBC to connect, but while trying to schedule jobs for glue, I cannot import PYODBC as it is not natively supported by AWS Glue, not sure how drivers will work in glue shell as well.
For AWS Glue use either Dataframe/DynamicFrame and specify the SQL Server JDBC driver. AWS Glue already contain JDBC Driver for SQL Server in its environment so you don't need to add any additional driver jar with glue job. 
df1=spark.read.format("jdbc").option("driver", "com.microsoft.sqlserver.jdbc.SQLServerDriver").option("url", url_src).option("dbtable", dbtable_src).option("user", userID_src).option("password", password_src).load()
if you are using a SQL instead of table:
df1=spark.read.format("jdbc").option("driver", "com.microsoft.sqlserver.jdbc.SQLServerDriver").option("url", url_src).option("dbtable", ("your select statement here") A).option("user", userID_src).option("password", password_src).load()
As an alternate solution you can also use jtds driver for SQL server in your python script running in AWS Glue
How to Connect to RDS Instance from AWS Glue Python Shell?