Django override default form error messages

To globally override the "required" error message, set the default_error_messages class attribute on Field:

# form error message override
from django.forms import Field
from django.utils.translation import ugettext_lazy
Field.default_error_messages = {
    'required': ugettext_lazy("This field is mandatory."),
}

This needs to happen before any fields are instantiated, e.g. by including it in settings.py.

Also come here from google and what I need is to overwrite the default required messages for all fields in my form rather than passing the error_messages argument everytime I defined new form fields. Also, I'm not ready yet to delve into i18n, this apps not required to be multilingual. The comment in this blog post is the closest to what I want:-

http://davedash.com/2008/11/28/custom-error-messages-for-django-forms/

For all form fields that has required messages, this is what I did:-

class MyForm(forms.Form):
    def __init__(self, *args, **kwargs):
        super(MyForm, self).__init__(*args, **kwargs)
        for k, field in self.fields.items():
            if 'required' in field.error_messages:
                field.error_messages['required'] = 'You have to field this.'

class MUserForm(MyForm):
    user = forms.CharField(
        label="Username",
    )
    ....

from django import forms
from django.utils.translation import gettext as _


class MyForm(forms.Form):
     # create form field
     subject = forms.CharField(required=True)

     # override one specific error message and leave the others unchanged
     # use gettext for translation
     subject.error_messages['required'] = _('Please enter a subject below.')