Wrap excerpt in try/except

excerpt can kick up socket.error and socket.timeout.  So we wrap it and
throw ExcerptErrors if things go awry.

oedipus/__init__.py

@@ -310,9 +310,11 @@ def excerpt(self, result):
         """Take a result and return the excerpt as a list of
         unicodes--one for each highlight_field in the order specified.
 
-        :raises ExcerptError: Raises an ``ExcerptError`` if ``excerpt``
-            was called before results were calculated or if
-            ``highlight_fields`` is not a subset of ``fields``.
+        :raises ExcerptError: Raises an ``ExcerptError`` if
+            ``excerpt`` was called before results were calculated, if
+            ``highlight_fields`` is not a subset of ``fields``, or if
+            there was a socket.error or socket.timeout trying to
+            retrieve the excerpt.
 
         """
         # This catches the case where results haven't been calculated.
@@ -348,8 +350,16 @@ def excerpt(self, result):
                 options[mem] = getattr(self.meta, 'excerpt_' + mem)
 
         sphinx = self._sphinx()
-        excerpt = sphinx.BuildExcerpts(
-            list(docs), self.meta.index, self._query, options)
+
+        try:
+            excerpt = sphinx.BuildExcerpts(
+                list(docs), self.meta.index, self._query, options)
+        except socket.error, msg:
+            # The sphinxapi exceptions suck, so raising our own and
+            # ignoring theirs doesn't make a big difference.
+            raise ExcerptError('Socket error building excerpt: %s!', msg)
+        except socket.timeout:
+            raise ExcerptError('Socket timeout error with excerpt!')
 
         # TODO: This assumes the data is in utf-8 which it might not
         # be depending on the backing database configuration.