理解回溯错误[DJANGO/PYTHON]

我试图理解一个回溯错误。见下文

我所做的是用Python操作PDF表单字段。 Im使用pdftk和fdfgen，仅使用pythonim操作PDF表单字段，如下示例

我的意见是：

def combine_pdfs(list_of_pdfs, outfile):
    '''
    Use pdftk to combine multiple pdfs into a signle pdf
    '''
    call = ['pdftk']
    call += list_of_pdfs
    call += ['cat', 'output']
    call += [outfile]
    print(" ".join(call))
    try:
        data_string = check_output(call).decode('utf8')
    except IOError:
        raise PdftkNotInstalledError('Could not locate PDFtk installation')
    return outfile

def get_fields(pdf_file):
    '''
    Use pdftk to get a pdf's fields as a string, parse the string
    and return the fields as a dictionary, with field names as keys
    and field values as values.
    '''
    fields = {}
    call = ['pdftk', pdf_file, 'dump_data_fields_utf8']
    try:
        data_string = check_output(call).decode('utf8')
    except IOError:
        raise PdftkNotInstalledError('Could not locate PDFtk installation')
    data_list = data_string.split('\r\n')
    if len(data_list) == 1:
        data_list = data_string.split('\n')
    for line in data_list:
        if line:
            re_object = match(r'(\w+): (.+)', line)
            if re_object is not None:
                if re_object.group(1) == 'FieldName':
                    key = re_object.group(2)
                    fields[key] = ''
                elif re_object.group(1) == 'FieldValue':
                    fields[key] = re_object.group(2)
    return fields

def write_pdf(source, fields, output, flatten=False):
    '''
    Take a source file path, list or dictionary of fdf fields, and
    output path, and create a filled-out pdf.
    '''
    fdf = forge_fdf(fdf_data_strings=fields)
    with NamedTemporaryFile(delete=False) as file:
        file.write(fdf)
    call = ['pdftk', source, 'fill_form', file.name, 'output', output]
    if flatten:
        call.append('flatten')
    try:
        check_output(call)
    except IOError:
        raise PdftkNotInstalledError('Could not locate PDFtk installation')
    remove(file.name)

class PdftkNotInstalledError(Exception):
    pass


def main(request,pk):
    if pk:
        obj = MyModel.objects.get(pk=pk)
        if obj.text == 'Secure':

            pdf_path = "/home/myproject/webapps/app/app/home/templates/home/fill.pdf"

            fields = get_fields(pdf_path)

            fields['F[0].P1[0].Name[0]'] = obj.name

            write_pdf(pdf_path,fields,'output.pdf')

        return HttpResponseRedirect('/Search')

url.py是：

url(r'^pdf_test/(?P<pk>[-\w]+)/$', views.main, name='pdf_test')

url（r'^pdf\u test/（？P[-\w]+）/$”，views.main，name='pdf\u test'）

url(r'^pdf_test/(?P<pk>[-\w]+)/$', views.main, name='pdf_test')