--- 0.11-stable.15868dcaea64/trac/mimeview/enscript.py	2008-11-27 02:25:18.000000000 +0100
+++ /home/joe/src/trac/0.11-stable/trac/mimeview/enscript.py	2008-11-27 02:21:05.000000000 +0100
@@ -119,11 +119,14 @@
 
     def __init__(self):
         self._types = None
+        self._available = True
 
     # IHTMLPreviewRenderer methods
 
     def get_quality_ratio(self, mimetype):
         # Extend default MIME type to mode mappings with configured ones
+        if not self._available:
+            return 0
         if not self._types:
             self._types = {}
             self._types.update(types)
@@ -140,6 +143,7 @@
 
         np = NaivePopen(cmdline, content.encode('utf-8'), capturestderr=1)
         if np.errorlevel or np.err:
+            self._available = False
             err = 'Running (%s) failed: %s, %s.' % (cmdline, np.errorlevel,
                                                     np.err)
             raise Exception, err