Appearance: Allow subclassing the TextArea widget

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

HISTORY.rst

@@ -11,6 +11,7 @@
 - Dependencies: Update Python dependencies version. Remove django suit
   as a dependency.
 - Appearance: Remove unused form_empty_label flag.
+- Appearance: Allow subclassing the text area widget.
 
 3.1.9 (2018-11-01)
 ==================

mayan/apps/appearance/templates/appearance/forms/widgets/textareadiv.html

@@ -1,2 +1,2 @@
 <pre name="{{ widget.name }}" {% include "django/forms/widgets/attrs.html" %}>
-{% if widget.value %}{{ widget.value }}{% endif %}</pre>
+{% block widget_value %}{% if widget.value %}{{ widget.value }}{% endif %}{% endblock %}</pre>