The dependency to the pycairo library is missing, which leads to the following error when starting the prewikka-httpd server:

Traceback (most recent call last):
  File "/usr/sbin/prewikka-httpd", line 35, in <module>
    from prewikka import Core, Request, siteconfig
  File "/usr/lib/python2.6/site-packages/prewikka/Core.py", line 23, in <module>
    import prewikka.views
  File "/usr/lib/python2.6/site-packages/prewikka/views/__init__.py", line 21, in <module>
    from prewikka.views import \
  File "/usr/lib/python2.6/site-packages/prewikka/views/stats.py", line 27, in <module>
    from prewikka import User, view, Chart, utils, resolve
  File "/usr/lib/python2.6/site-packages/prewikka/Chart.py", line 29, in <module>
    from prewikka import utils, siteconfig, cairoplot
  File "/usr/lib/python2.6/site-packages/prewikka/cairoplot.py", line 34, in <module>
    import cairo
ImportError: No module named cairo