dbConnect(dbDriver("PostgreSQL"),
          user = user,
          password = password,
          host = host,
          dbname = "dbname=dbname sslmode=require",
          port = 5432)

Error in postgresqlNewConnection(drv, ...) :
  RS-DBI driver: (could not connect user@host:5432 on dbname "dbname": sslmode value "require" invalid when SSL support is not compiled in)