add GridFSError as base exception class for gridfs errors

gridfs/errors.py

@@ -14,7 +14,16 @@
 
 """Exceptions raised by the :mod:`gridfs` package"""
 
-class CorruptGridFile(Exception):
+from pymongo.errors import PyMongoError
+
+
+class GridFSError(PyMongoError):
+    """Base class for all GridFS exceptions.
+
+    .. versionadded:: 1.4+
+    """
+
+class CorruptGridFile(GridFSError):
     """Raised when a :class:`~gridfs.grid_file.GridFile` instance is
     malformed.
     """

pymongo/objectid.py

@@ -20,7 +20,7 @@ import datetime
 try:
     import hashlib
     _md5func = hashlib.md5
-except: # for Python < 2.5
+except ImportError: # for Python < 2.5
     import md5
     _md5func = md5.new
 import os