release 3.13.3
configure.ac: post release version bump to 3.13.4
tests: Ignore stock-id usage warnings

Add ignore_glib_warnings context manager for easily ignoring warnings
caused by stock-id usage. Even though stock-id is deprecated, we still
need to test the related Python binding overrides.
tests: Remove usage of deprecated "schema" property in GSettings creation

Use new and new_with_path instead as the schema property was causing a
hard warning which fails the test suite.
tests: Ignore warnings for GtkAlignment

This was causing unittests to bail. Even though this is deprecated,
we still need to test its usage in the context of pygtkcompat.
pyflakes: Fix legacy print and exception usage under Python 3

Fix print statements and legacy exception usage in examples.

https://bugzilla.gnome.org/show_bug.cgi?id=731042