jinja2.exceptions.UndefinedError: 'skin' is undefined

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I am getting this error after some time starting the server, what might be the reason? using code from github

Traceback (most recent call last):
  File "/home/myuser/projects/venv/local/lib/python2.7/site-packages/Django-1.5-py2.7.egg/django/core/handlers/wsgi.py", line 255, in __call__
    response = self.get_response(request)
  File "/home/myuser/projects/venv/local/lib/python2.7/site-packages/Django-1.5-py2.7.egg/django/core/handlers/base.py", line 178, in get_response
    response = self.handle_uncaught_exception(request, resolver, sys.exc_info())
  File "/home/myuser/projects/venv/local/lib/python2.7/site-packages/Django-1.5-py2.7.egg/django/core/handlers/base.py", line 224, in handle_uncaught_exception
    return callback(request, **param_dict)
  File "/home/myuser/projects/venv/local/lib/python2.7/site-packages/Django-1.5-py2.7.egg/django/utils/decorators.py", line 91, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "/home/myuser/projects/venv/local/lib/python2.7/site-packages/Django-1.5-py2.7.egg/django/views/defaults.py", line 41, in server_error
    return http.HttpResponseServerError(template.render(Context({})))
  File "/home/myuser/projects/venv/local/lib/python2.7/site-packages/Coffin-0.3.8-py2.7.egg/coffin/template/__init__.py", line 55, in render
    return super(Template, self).render(**context)
  File "/home/myuser/projects/venv/local/lib/python2.7/site-packages/Jinja2-2.7.1-py2.7.egg/jinja2/environment.py", line 969, in render
    return self.environment.handle_exception(exc_info, True)
  File "/home/myuser/projects/venv/local/lib/python2.7/site-packages/Jinja2-2.7.1-py2.7.egg/jinja2/environment.py", line 742, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "./askbot/templates/500.html", line 1, in top-level template code
    {% extends "two_column_body.html" %}
  File "./askbot/templates/two_column_body.html", line 1, in top-level template code
    {% extends "base.html" %}
  File "./askbot/templates/base.html", line 27, in top-level template code
    {% include "meta/html_head_stylesheets.html" %}
  File "./askbot/templates/meta/html_head_stylesheets.html", line 7, in top-level template code
    {% compress css %}
  File "/home/myuser/projects/venv/local/lib/python2.7/site-packages/django_compressor-1.2-py2.7.egg/compressor/contrib/jinja2ext.py", line 40, in _compress
    original_content = caller()
  File "./askbot/templates/meta/html_head_stylesheets.html", line 9, in template
    {{ skin.get_extra_css_link() }}
  File "/home/myuser/projects/venv/local/lib/python2.7/site-packages/Jinja2-2.7.1-py2.7.egg/jinja2/environment.py", line 397, in getattr
    return getattr(obj, attribute)
jinja2.exceptions.UndefinedError: 'skin' is undefined