psycopg2.errors.InFailedSqlTransaction：当前事务已中止，在事务块结束之前忽略命令，不知道如何修复

我试图使用psycopg2将数据插入到数据库中，但我遇到了一个奇怪的错误。我尝试了一些方法，但没有奏效。这是我的代码：

def insert_transaction():
global username
now = datetime.now()
date_checkout = datetime.today().strftime('%d-%m-%Y')
time_checkout = now.strftime("%H:%M:%S")

username = "Peter1"

connection_string = "host='localhost' dbname='Los Pollos Hermanos' user='postgres' password='******'"
conn = psycopg2.connect(connection_string)
cursor = conn.cursor()
try:
    query_check_1 = """(SELECT employeeid FROM employee WHERE username = %s);"""
    cursor.execute(query_check_1, (username,))
    employeeid = cursor.fetchone()[0]
    conn.commit()
except:
    print("Employee error")

try:
    query_check_2 = """SELECT MAX(transactionnumber) FROM Transaction"""
    cursor.execute(query_check_2)
    transactionnumber = cursor.fetchone()[0] + 1
    conn.commit()
except:
    transactionnumber = 1

""""---------INSERT INTO TRANSACTION------------"""


query_insert_transaction = """INSERT INTO transactie (transactionnumber, date, time, employeeemployeeid)
                    VALUES (%s, %s, %s, %s);"""
data = (transactionnumber, date_checkout, time_checkout, employeeid)
cursor.execute(query_insert_transaction, data)
conn.commit()
conn.close()

这是错误：

", line 140, in insert_transaction
cursor.execute(query_insert_transaction, data) psycopg2.errors.InFailedSqlTransaction: current transaction is aborted, commands ignored until end of transaction block