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espressif/esp-idf / components/driver/include/driver/uart.h defines the API:
esp_err_t uart_set_pin(uart_port_t uart_num, int tx_io_num, int rx_io_num, int **rts_io_num**, int **cts_io_num**);
uartSetPins uses that api but alls it with swapped CTS/RTS pins as its API uses a different pin ordering: 
uart_set_pin(uart->num, txPin, rxPin, **ctsPin**, **rtsPin**); 

This fixes the wrong order in the function uartSetPins