Static page generator fails occassionally on new boxes

[matze]

www@web2:~$ PYTHONPATH=/opt/cms:/opt/sitescripts python -m cms.bin.generate_static_pages /home/www/web.adblockplus.org /var/www
/adblockplus.org
Traceback (most recent call last):
  File "/usr/lib/python2.7/runpy.py", line 162, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/lib/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/opt/cms/cms/bin/generate_static_pages.py", line 150, in <module>
    generate_pages(repo, output_dir)
  File "/opt/cms/cms/bin/generate_static_pages.py", line 96, in generate_pages
    params = get_page_params(source, locale, page, format)
  File "/opt/cms/cms/utils.py", line 73, in get_page_params
    params["head"], params["body"] = converter()
  File "/opt/cms/cms/converters.py", line 267, in __call__
    result = self.get_html(self._params[self._key])
  File "/opt/cms/cms/converters.py", line 362, in get_html
    module = template.make_module(self._params)
  File "/usr/lib/python2.7/dist-packages/jinja2/environment.py", line 938, in make_module
    return TemplateModule(self, self.new_context(vars, shared, locals))
  File "/usr/lib/python2.7/dist-packages/jinja2/environment.py", line 994, in __init__
    self._body_stream = list(template.root_render_func(context))
  File "<template>", line 54, in root
  File "/usr/lib/python2.7/dist-packages/jinja2/runtime.py", line 180, in call
    return __obj(*args, **kwargs)
  File "<string>", line 187, in get_browser_versions
  File "<string>", line 169, in open_cache_file
  File "/usr/lib/python2.7/os.py", line 157, in makedirs
    mkdir(name, mode)
OSError: [Errno 13] Permission denied: '/var/cache/web.adblockplus.org'