Only point releases are support to avoid breaking code (though they sometime do).

Minor release may break code, though it should be rare. Python 3.7 reserves 'async' and 'await' as keywords so assignments like "async = 3", which worked in 3.6, will now fail.

Python has a deprecation warning system which can detect cases like this, but it must be enabled:

  % python -Wall
  Python 3.6.5 (v3.6.5:f59c0932b4, Mar 28 2018, 05:52:31)
  [GCC 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.57)] on darwin
  Type "help", "copyright", "credits" or "license" for more information.
  >>> async = 3
  <stdin>:1: DeprecationWarning: 'async' and 'await' will become
  reserved keywords in Python 3.7