NoReverseMatch with keyword argument uidb64 with Django 2.0

I can’t understand why my code doesn’t work. Before it worked, but now, when I run the server and test, the code does not work.

When the user is registering, I send him activation email, like this:

def send_activation_email(serializer, request, user):
    current_site = get_current_site(request)
    message = render_to_string('acc_active_email.html', {
        'user': user,
        'domain': current_site.domain,
        'uid': urlsafe_base64_encode(force_bytes(user.pk)),
        'token': account_activation_token.make_token(user),
    })
    mail_subject = 'Activate your blog account.'
    to_email = serializer.data['email']

    email = EmailMessage(mail_subject, message, to=[to_email])
    email.send()

acc_active_email.html

{% autoescape off %}
Hi {{ user.username }},
Please click on the link to confirm your registration,

http://{{ domain }}{% url 'activate' uidb64=uid token=token %}
{% endautoescape %}

and my url file

.
.
    url(r'^activate/(?P<uidb64>[0-9A-Za-z_-]+)/(?P<token>[0-9A-Za-z]{1,13}-[0-9A-Za-z]{1,20})/$',
        views.activate_account, name='activate'),
.
.

but I have this error:

Exception Type:     NoReverseMatch
Exception Value:    

Reverse for 'activate' with keyword arguments '{'uidb64': b'NDM', 'token': '4qz-8f770502bd8b02786da9'}' not found. 1 pattern(s) tried: ['activate/(?P<uidb64>[0-9A-Za-z_\-]+)/(?P<token>[0-9A-Za-z]{1,13}-[0-9A-Za-z]{1,20})/$']

highlights this line http://{{ domain }}{% url 'activate' uidb64=uid token=token %}

Answer

In Django 2.0 and 2.1 you should call decode() after base64 encoding the uid, to convert it to a string:

message = render_to_string('acc_active_email.html', {
    'user': user,
    'domain': current_site.domain,
    'uid': urlsafe_base64_encode(force_bytes(user.pk)).decode(),
    'token': account_activation_token.make_token(user),
})

See the note in the Django 2.0 release notes for more info.

In Django 2.2+, urlsafe_base64_encode returns a string, so there is no need to decode.

message = render_to_string('acc_active_email.html', {
    'user': user,
    'domain': current_site.domain,
    'uid': urlsafe_base64_encode(force_bytes(user.pk)),
    'token': account_activation_token.make_token(user),
})

It should be possible to write code that is compatible with Django <= 1.11, 2.0-2.1, and 2.2+, by using force_text. Note the following is untested.

from django.utils.encoding import force_text

message = render_to_string('acc_active_email.html', {
    'user': user,
    'domain': current_site.domain,
    'uid': force_text(urlsafe_base64_encode(force_bytes(user.pk))),
    'token': account_activation_token.make_token(user),
})

You can drop the force_text and use the second code snippet once you drop support for Django < 2.2.