diff --git a/session.vim b/session.vim
index 9d326c5822..f33590c838 100644
--- a/session.vim
+++ b/session.vim
@@ -1,5 +1,5 @@
 " Project wide builtins
-let g:pyflakes_builtins += ["dynamic_property"]
+let g:pyflakes_builtins += ["dynamic_property", "__"]
 
 python << EOFPY
 import os
diff --git a/src/calibre/ebooks/metadata/opf2.py b/src/calibre/ebooks/metadata/opf2.py
index 952978fc36..dd3128edef 100644
--- a/src/calibre/ebooks/metadata/opf2.py
+++ b/src/calibre/ebooks/metadata/opf2.py
@@ -508,11 +508,8 @@ class OPF(object):
                     toc.partition('#')[0], toc.partition('#')[-1]
                 self.toc.read_html_toc(toc)
         except:
-            raise
             pass
 
-
-
     def get_text(self, elem):
         return u''.join(self.CONTENT(elem) or self.TEXT(elem))
 
diff --git a/src/calibre/ebooks/oeb/base.py b/src/calibre/ebooks/oeb/base.py
index 940b124d88..f7f02f7660 100644
--- a/src/calibre/ebooks/oeb/base.py
+++ b/src/calibre/ebooks/oeb/base.py
@@ -201,6 +201,9 @@ def urlnormalize(href):
 class OEBError(Exception):
     pass
 
+class NotHTML(OEBError):
+    pass
+
 
 class FauxLogger(object):
     def __getattr__(self, name):
@@ -538,7 +541,7 @@ class Manifest(object):
                         data = etree.fromstring(data, parser=RECOVER_PARSER)
             # Force into the XHTML namespace
             if barename(data.tag) != 'html':
-                raise OEBError(
+                raise NotHTML(
                     'File %r does not appear to be (X)HTML' % self.href)
             elif not namespace(data.tag):
                 data.attrib['xmlns'] = XHTML_NS