{% autoescape on %}
{% for row in diff %}
    {% for sign, text in row %}
        {% if sign == '+' and text %}
            <pre style="text-decoration: none; display: inline; font-family: sans-serif; background: #e6ffe6">{{ text }}</pre>
        {% endif %}
        {% if sign == '-' and text %}
            <pre style="text-decoration: none; display: inline; font-family: sans-serif; background: #ffe6e6">{{ text }}</pre>
        {% endif %}
        {% if sign == '=' %}
            <pre style="text-decoration: none; display: inline; font-family: sans-serif;">{{ text }}</pre>
        {% endif %}
        {% if sign == '.' %}
            ...
        {% endif %}
    {% endfor %}
    <br>
{% endfor %}
{% endautoescape %}