Getting a redshift error while using RDS Postgres with PySpark - postgresql

Question

I'm trying to load data in PySpark from a normal Amazon RDS Postgres DB:
df = sqlCtx.read.format('jdbc').option('url', f"jdbc:postgresql://{DB_HOSTNAME}:{DB_PORT}/{DATABASE}?ssl=false").option("dbtable","public.pc").option("user", DB_USERNAME).option("password", DB_PASSWORD).load()
But strangely, I'm getting this authentication error which looks like it's using redshift libraries (even though this is not a redshift db):
Py4JJavaError: An error occurred while calling o81.load.
: java.sql.SQLException: [Amazon](500101) Error authenticating with database:
Authentication: isAuthenticationOK - false
isKerberos5Required - false
isClearTextPasswordRequired - false
isMD5PasswordRequired - false
isSCMCredentialsMessageRequired - false
isGSSAPIAuthenticationRequired - false
isSSPIAuthenticationRequired - false
isGSSContinue - false
at com.amazon.redshift.client.PGClient.startSession(Unknown Source)
at com.amazon.redshift.client.PGClient.<init>(Unknown Source)
at com.amazon.redshift.core.PGJDBCConnection.connect(Unknown Source)
at com.amazon.jdbc.common.BaseConnectionFactory.doConnect(Unknown Source)
at com.amazon.jdbc.common.AbstractDriver.connect(Unknown Source)
I also know my credentials are valid, as they work with a DB explorer app as well as with the psycopg2 library. Any ideas?