How to customize django rest auth password reset email content/template

You can inherit PasswordResetSerializer and override the get_email_options method. For example:

from rest_auth.serializers import PasswordResetSerializer


class CustomPasswordResetSerializer(PasswordResetSerializer):
    def get_email_options(self):
        return {
            'subject_template_name': 'registration/password_reset_subject.txt',
            'email_template_name': 'registration/password_reset_message.txt',
            'html_email_template_name': 'registration/'
                                    'password_reset_message.html',
            'extra_email_context': {
                'pass_reset_obj': self.your_extra_reset_obj
            }
        }

I recently needed to implement the same thing in one of my projects and could not find a thorough answer anywhere.

So I'm leaving my solution here for anyone who needs it in the future.

Expanding on mariodev's suggestion:

1. Subclass PasswordResetSerializer and override save method.

yourproject_app/serializers.py

from django.conf import settings
from rest_auth.serializers import PasswordResetSerializer as _PasswordResetSerializer

class PasswordResetSerializer(_PasswordResetSerializer):
    def save(self):
        request = self.context.get('request')
        opts = {
            'use_https': request.is_secure(),
            'from_email': getattr(settings, 'DEFAULT_FROM_EMAIL'),

            ###### USE YOUR TEXT FILE ######
            'email_template_name': 'example_message.txt',

            'request': request,
        }
        self.reset_form.save(**opts)

2. Configure AUTH_USER_MODEL

yourproject/settings.py

###### USE YOUR USER MODEL ######
AUTH_USER_MODEL = 'yourproject_app.ExampleUser'

3. Connect custom PasswordResetSerializer to override default

yourproject/settings.py

REST_AUTH_SERIALIZERS = {
    'PASSWORD_RESET_SERIALIZER': 
        'yourproject_app.serializers.PasswordResetSerializer',
}

4. Add the path to the directory where your custom email message text file is located to TEMPLATES

yourproject/settings.py

TEMPLATES = [
    {
        ...
        'DIRS': [os.path.join(BASE_DIR, 'yourproject/templates')],
        ...
    }
]

5. Write custom email message (default copied from Django)

yourproject/templates/example_message.txt

{% load i18n %}{% autoescape off %}
{% blocktrans %}You're receiving this email because you requested a password reset 
for your user account at {{ site_name }}.{% endblocktrans %}

{% trans "Please go to the following page and choose a new password:" %}
{% block reset_link %}
{{ protocol }}://{{ domain }}{% url 'password_reset_confirm' uidb64=uid token=token %}
{% endblock %}
{% trans "Your username, in case you've forgotten:" %} {{ user.get_username }}

{% trans "Thanks for using our site!" %}

{% blocktrans %}The {{ site_name }} team{% endblocktrans %}

{% endautoescape %}

UPDATE: This solution was written for an older version of django-rest-auth (v0.6.0). As I can tell from the comments, it seems there have been some updates made to the source package that more readily handle custom email templates out-of-box. It is always better to use methods defined in a package rather than overriding them like in my solution. Though once a necessity, it may not be so any longer.