Generalize tuple() to work nicely with iterators.

NEEDS DOC CHANGES.
This one surprised me!  While I expected tuple() to be a no-brainer, turns
out it's actually dripping with consequences:
1. It will *allow* the popular PySequence_Fast() to work with any iterable
   object (code for that not yet checked in, but should be trivial).
2. It caused two std tests to fail.  This because some places used
   PyTuple_Sequence() (the C spelling of tuple()) as an indirect way to test
   whether something *is* a sequence.  But tuple() code only looked for the
   existence of sq->item to determine that, and e.g. an instance passed
   that test whether or not it supported the other operations tuple()
   needed (e.g., __len__).  So some things the tests *expected* to fail
   with an AttributeError now fail with a TypeError instead.  This looks
   like an improvement to me; e.g., test_coercion used to produce 559
   TypeErrors and 2 AttributeErrors, and now they're all TypeErrors.  The
   error details are more informative too, because the places calling this
   were *looking* for TypeErrors in order to replace the generic tuple()
   "not a sequence" msg with their own more specific text, and
   AttributeErrors snuck by that.

1 files changed, 2 insertions, 2 deletions

diff --git a/Misc/NEWS b/Misc/NEWS
index 01455d2..d838c0f 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -24,9 +24,9 @@ Core
     min()
     reduce()
     XXX TODO string.join(), unicode.join()
-    XXX TODO tuple()
+    tuple()
     XXX TODO zip()
-    XXX TODO 'x in y' (!) (?)
+    XXX TODO 'x in y'
 
 What's New in Python 2.1 (final)?
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