- add support for self-referential foreign keys to move over as well when
the table name is changed.

of the "constants" :func:`.null`, :func:`.true`, and :func:`.false`
has been reverted.   These functions returning a "singleton" object
had the effect that different instances would be treated as the
same regardless of lexical use, which in particular would impact
the rendering of the columns clause of a SELECT statement.
fixes #3170

and parameters are not displayed if None, reducing confusion for
error messages that weren't related to a statement.  The full
module and classname for the DBAPI-level exception is displayed,
making it clear that this is a wrapped DBAPI exception.  The
statement and parameters themselves are bounded within a bracketed
sections to better isolate them from the error message and from
each other.
fixes #3172

the  python 3 merge, now does not expect percent signs (e.g.
as used as the modulus operator and others) to be doubled,
even when using the "pyformat" bound parameter format (this
change is not documented by Mysqlconnector).  The dialect now
checks for py2k and for mysqlconnector less than version 2.0
when detecting if the modulus operator should be rendered as
``%%`` or ``%``.
- Unicode SQL is now passed for MySQLconnector version 2.0 and above;
for Py2k and MySQL < 2.0, strings are encoded.  Note that mysqlconnector
as of 2.0.1 appears to have a bug with unicode DDL on py2k, so the tests here
are skipping until we observe it's fixed.
- take out profiling on mysqlconnector, callcounts vary too much with
its current development speed

defaults if otherwise unspecified; the limitation where non-
server column defaults aren't included in an INSERT FROM
SELECT is now lifted and these expressions are rendered as
constants into the SELECT statement.

the sql package would fail to ``__repr__()`` successfully,
due to a missing ``description`` attribute that would then invoke
a recursion overflow when an internal AttributeError would then
re-invoke ``__repr__()``.
fixes #3195