Tightens exception catches for preview manager calls

tracim/tracim/controllers/content.py

 
 from cgi import FieldStorage
 from depot.manager import DepotManager
+from preview_generator.exception import PreviewGeneratorException
 from preview_generator.manager import PreviewManager
 from sqlalchemy.orm.exc import NoResultFound
 import tg
         nb_page = 0
         try:
             nb_page = preview_manager.get_page_nb(file_path=file_path)
-        except:
+        except PreviewGeneratorException:
             pass
         preview_urls = []
         for page in range(int(nb_page)):

tracim/tracim/controllers/page.py

 import tg
 from tg import expose
 from tg import tmpl_context
+from preview_generator.exception import PreviewGeneratorException
 from preview_generator.manager import PreviewManager
 
 from tracim.config.app_cfg import CFG
                                                     height=size,
                                                     width=size)
             with open(path, 'rb') as large:
-                return large.read()
-        except:
-            pass
+                result = large.read()
+        except PreviewGeneratorException:
+            result = None
+        return result
 
     @expose(content_type='image/jpeg')
     def high_quality(self,