FastAPI Error Handling : Need to handle Primary Key and Unique Key Violations but the Code never runs the Exception Handling part

Question

@app.post(path='/create')
def create_record(request: Request,sid: str = Form(...), name: str = Form(...),last_name: str = Form (...), email: str = Form(...),
                   add: str = Form(...), gpa: str = Form(...)):
    import mysql.connector
    cnx = mysql.connector.connect(user='NOPE', host='NOPE', database='NOPE', password='NOPE')
    cursor = cnx.cursor()
    query = "INSERT INTO `StudentInfo`.`Student` (`StudentId`, `FirstName`, `LastName`, `Email`, `Address`, `GPA`) VALUES ('%s', '%s','%s','%s','%s','%s');"%(sid ,name ,last_name ,email ,add ,gpa)
    print(query)
    if query is None:
        raise HTTPException(status_code=500, detail="Student ID or email already exists, please check what you've "
                                                    "entered and retry or contact Administrator.")
    else:
        cursor.execute(query)
        cnx.commit()
        cursor.close()
        return templates.TemplateResponse("extend_5.html", {"request": request})

So basically, the code always shows the "Internal Server Error" Page instead of what I wrote up there. Am I not catching the exception correctly?

When Someone enters the same studentid or email it should show, "Student ID or email already exists, please check...."

I am very new to Web Dev and FastAPI, what am I doing wrong?