Two changes to from...import:

1) "from M import X" now works even if M is not a real module; it's
   basically a getattr() operation with AttributeError exceptions
   changed into ImportError.

2) "from M import *" now looks for M.__all__ to decide which names to
   import; if M.__all__ doesn't exist, it uses M.__dict__.keys() but
   filters out names starting with '_' as before.  Whether or not
   __all__ exists, there's no restriction on the type of M.