Python 3.6.3rc1 and 3.7.0a1 now available for testing and more

The Python build factories have been busy the last several weeks preparing
our fall lineup of releases.  Today we are happy to announce three
additions: 3.6.3rc1, 3.7.0a1, and 3.3.7 final, which join last weekend's
2.7.14 and last month's 3.5.4 bug-fix releases and 3.4.7 security-fix
update (see all downloads).

1. Python 3.6.3rc1 is the first release candidate for Python 3.6.3, the next
maintenance release of Python 3.6.  While 3.6.3rc1 is a preview release and,
thus, not intended for production environments, we encourage you to explore
it and provide feedback via the Python bug tracker (https://bugs.python.org).
3.6.3 is planned for final release on 2017-10-02 with the next maintenance
release expected to follow in about 3 months.  You can find Python 3.6.3rc1
and more information here:
    https://www.python.org/downloads/release/python-363rc1/

2. Python 3.7.0a1 is the first of four planned alpha releases of Python 3.7,
the next feature release of Python.  During the alpha phase, Python 3.7
remains under heavy development: additional features will be added
and existing features may be modified or deleted.  Please keep in mind
that this is a preview release and its use is not recommended for
production environments.  The next preview release, 3.7.0a2, is planned
for 2017-10-16. You can find Python 3.7.0a1 and more information here:
    https://www.python.org/downloads/release/python-370a1/

3. Python 3.3.7 is also now available.  It is a security-fix source-only release
and is expected to be the final release of any kind for Python 3.3.x before it
reaches end-of-life status on 2017-09-29, five years after its initial release.
Because 3.3.x has long been in security-fix mode, 3.3.7 may no longer build
correctly on all current operating system releases and some tests may fail.
If you are still using Python 3.3.x, we strongly encourage you to upgrade
now to a more recent, fully supported version of Python 3.  You can find
Python 3.3.7 here:
   https://www.python.org/downloads/release/python-337/