Print or notify ON CONFLICT on INSERT

Question

I am avoiding duplicates with ON CONFLICT, but I would like to print something and know that a conflict just occurred , how can I do that with the current query ?

connection = engine.connect()

# APPEND TO STAGING TEMP TABLE
df.to_sql('temp_insert', connection, if_exists ='replace')

# STRING OF COMMA SEPARATED COLUMNS IN CASE NOT ALL COLS EXIST
cols = ", ".join(df.columns)

sql = (
    '''INSERT INTO {table_name} ({cols}) 
    SELECT {cols} FROM temp_insert 
    ON CONFLICT DO NOTHING'''.format(table_name=table_name,cols=cols)
)

result = connection.execute(sql) #could I know here ???
connection.close()