Use proper cached static image for unknown file

boards/models/attachment/viewers.py

@@ -1,39 +1,40 b''
 from django.template.defaultfilters import filesizeformat
+from django.templatetags.static import static
 
 
 class AbstractViewer:
     def __init__(self, file, file_type):
         self.file = file
         self.file_type = file_type
 
     @staticmethod
     def get_viewer(file_type, file):
         for viewer in VIEWERS:
             if viewer.supports(file_type):
                 return viewer(file)
         return AbstractViewer(file)
 
     @staticmethod
     def supports(file_type):
         return true
 
     def get_view(self):
         return '<div class="image"><a href="{}">'\
-               '<img src="/static/images/file.png" width="200" height="150"/>'\
+               '<img src="{}" width="200" height="150"/>'\
                '</a>'\
                '<div class="image-metadata">{}, {}</div>'\
-               '</div>'.format(self.file.url, self.file_type,
+               '</div>'.format(self.file.url, static('images/file.png'), self.file_type,
                        filesizeformat(self.file.size))
 
 
 class WebmViewer(AbstractViewer):
     @staticmethod
     def supports(file_type):
         return file_type == 'webm'
 
     def get_view(self):
         return '<div class="image">'\
                '<video width="200" height="150" controls/>'\
                '<source src="{}">'\
                '</div>'.format(self.file.url)