admin.py

from django.core.exceptions import PermissionDenied
from django.contrib import admin
from crm.models import Customer


class ReadPermissionModelAdmin(admin.ModelAdmin):
    def has_change_permission(self, request, obj=None):
        if getattr(request, 'readonly', False):
            return True
        return super(ReadPermissionModelAdmin, self).has_change_permission(request, obj)

    def changelist_view(self, request, extra_context=None):
        try:
            return super(ReadPermissionModelAdmin, self).changelist_view(
                request, extra_context=extra_context)
        except PermissionDenied:
            pass
        if request.method == 'POST':
            raise PermissionDenied
        request.readonly = True
        return super(ReadPermissionModelAdmin, self).changelist_view(
            request, extra_context=extra_context)

    def change_view(self, request, object_id, extra_context=None):
        try:
            return super(ReadPermissionModelAdmin, self).change_view(
                request, object_id, extra_context=extra_context)
        except PermissionDenied:
            pass
        if request.method == 'POST':
            raise PermissionDenied
        request.readonly = True
        return super(ReadPermissionModelAdmin, self).change_view(
            request, object_id, extra_context=extra_context)


class CustomerAdmin(ReadPermissionModelAdmin):
    pass


admin.site.register(Customer, CustomerAdmin)