No wkhtmltopdf executable found: "b''" If this file exists please check that this process can read it

After hosting my Django application on Heroku while I try to download dynamic pdf my Django app's wkhtmltopdf causes this error.

In local machine(Ubuntu) I've applied

sudo apt-get install wkhtmltopdf

I've also added Aptfile with my project directory so that Heroku installs those dependency and requirements while building the application.

Aptfile:

wkhtmltopdf

But unfortunately Heroku don't even builds the app with the given dependency.

I've also tried to install it by running Heroku bash but Heroku prevents.

W: Not using locking for read only lock file /var/lib/dpkg/lock-frontend
W: Not using locking for read only lock file /var/lib/dpkg/lock
E: Unable to locate package wkhtmltopdf

My code for generating pdf is:

def pdf_generation(request, pk):
    ''' Will generate PDF file from the html template '''
    template = get_template('bankApp/print_view.html')
    withdraw_obj = get_object_or_404(Withdraw, id=pk)
    year_month_day = withdraw_obj.withdrawn_on.split('-')
    day = year_month_day[2]
    month = year_month_day[1]
    year = year_month_day[0]
    word_amount = f'{num2words(withdraw_obj.withdrawn_amount)} Only'
    date = f'{day}{month}{year}'


    html = template.render({
        'pay_to': withdraw_obj.paid_to,
        'date': date,
        'amount': withdraw_obj.withdrawn_amount,
        'amount_word': word_amount
    })
    options = {
        'page-size': 'A4',
        'margin-top': '0.0in',
        'margin-right': '0.0in',
        'margin-bottom': '0.0in',
        'margin-left': '0.0in',
        'encoding': 'UTF-8',
    }


    pdf = pdfkit.from_string(html, False, options=options)
    response = HttpResponse(pdf, content_type='application/pdf')
    response['Content-Disposition'] = 'attachment;\
       filename="print.pdf"'

    return response

Server Error:

OSError at /bank/pdf/print/2

No wkhtmltopdf executable found: "b''"
If this file exists please check that this process can read it. Otherwise please install wkhtmltopdf - https://github.com/JazzCore/python-pdfkit/wiki/Installing-wkhtmltopdf

Request Method:     GET
Request URL:    https://issue-cheque.herokuapp.com/bank/pdf/print/2
Django Version:     3.1.7
Exception Type:     OSError
Exception Value:    

No wkhtmltopdf executable found: "b''"
If this file exists please check that this process can read it. Otherwise please install wkhtmltopdf - https://github.com/JazzCore/python-pdfkit/wiki/Installing-wkhtmltopdf

Exception Location:     /app/.heroku/python/lib/python3.6/site-packages/pdfkit/configuration.py, line 27, in __init__
Python Executable:  /app/.heroku/python/bin/python
Python Version:     3.6.13
Python Path:    

['/app/.heroku/python/bin',
 '/app',
 '/app/.heroku/python/lib/python36.zip',
 '/app/.heroku/python/lib/python3.6',
 '/app/.heroku/python/lib/python3.6/lib-dynload',
 '/app/.heroku/python/lib/python3.6/site-packages']

Server time:    Sat, 13 Mar 2021 10:51:55 +0000