After investigations, commit the proposed patch by kklimonda presented with the following introduction : cm/templates/site/login_form.html template uses a relative url for the form action, which seems to break deployment in the subfolder when trailing slash is missing (the form redirects to the upper folder breaking login). Using {% url login %} (as in the attached patch) instead would fix the issue.

{% extends "email/base_email.txt" %}{% load i18n %}

{% block content %}
{% blocktrans %}Your text "{{ title }}" has been created.{% endblocktrans %}

{% blocktrans %}To publish it click on the following link:{% endblocktrans %}
{{ site_url }}{{ publish_url }} 
{% endblock %}