What method does Python 2 use to print tuples?

Python's print statement normally seems to print the repr() of its input. Tuples don't appear to be an exception:

>>> print (1, 2, 3)
(1, 2, 3)
>>> print repr((1, 2, 3))
(1, 2, 3)

But then I stumbled across some strange behavior while messing around with CPython's internals. In short: if you trick Python 2 into creating a self-referencing tuple, printing it directly behaves completely differently from printing its repr() / str() / unicode() representations.

>>> print outer   # refer to the link above
((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((
((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((
... many lines later ...
((((((((((Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
MemoryError: stack overflow
>>> print repr(outer)
((...),)
>>> print str(outer)
((...),)
>>> print unicode(outer)
((...),)

So what exactly is print doing? In an attempt to answer this question myself, I referred to the language reference:

6.6. The print statement

print evaluates each expression in turn and writes the resulting object to standard output (see below). If an object is not a string, it is first converted to a string using the rules for string conversions.

And the rules for string conversions are:

5.2.9. String conversions

A string conversion is an expression list enclosed in reverse (a.k.a. backward) quotes:

string_conversion ::=  "`" expression_list "`"

But enclosing outer in back quotes has the same result as calling repr() and friends. No dice. So what the heck is print actually doing behind the scenes?

(Interestingly, the behavior is "fixed" in Python 3: printing a self-referencing tuple gives the ellipsis-truncated form.)