BUG: Provide asset data for multiple symbol error.

Fix a change in the information given to the multiple symbol error
during the recent sqlite change to the asset finder.

Instead of the string of sids, return full asset information about the
available options, since internal code relied on the full data.

zipline/assets/assets.py

@@ -376,8 +376,13 @@ class AssetFinder(object):
             elif not data:
                 raise SymbolNotFound(symbol=symbol)
             else:
+                options = []
+                for row in data:
+                    sid = row[0]
+                    asset = self._retrieve_equity(sid)
+                    options.append(asset)
                 raise MultipleSymbolsFound(symbol=symbol,
-                                           options=str(data))
+                                           options=options)
 
     def lookup_symbol(self, symbol, as_of_date, fuzzy=False):
         """