So user have more control on whether to build it or not

Also make it conditional on the Gtk.Widget method existing since that was only
added with gtk 3.20 and we support 3.18+.

Fixes #371. Gtk.Button.set_focus_on_click and Gtk.Button.get_focus_on_click
are deprecated since version 3.20. This override calls the Gtk.Widget methods
so that users don't get a deprecation message.
Signed-off-by: Dan Yeaw <dan@yeaw.me>

See gtk commit c1f71ee3e8add0c8e43445b888719ac85a743583. There are now
top_level windows only.

A new gtk4 test is added to check that windows are correctly created
and work from builder.

See gtk commit 2244eeb7270f5a0b351aae98c19ddbc4d4b5bea7.

init_template method is automatically called when a widget is
created and it is not supposed to be called multiple times. That is
why this method is turned into a no-op after its first call via a
lambda function.

init_template can still be called after a widget creation (and it is
supposed to do nothing). However, a second call will result in a crash
because the lambda function has a parameter while init_template is not
supposed to have any parameter.

This issue is fixed by removing the parameter of the lambda function.

A new test is also added to assert that a second init_template call
does nothing.

When a widget is inside a template it is created through a
g_object_new and does not have a python wrapper when
pygobject__g_instance_init is called. In that case, a wrapper is
created and the "__init__" method is called to instantiate it. Then,
"init_template" is called to init its own template (if it exists).

However, "init_template" needs to be called before the object
constructor in order to create and instantiate all its children,
signals and properties.

This issue is fixed by calling init_template before the contructor if
the python object has been created through g_object_new.

A new test for the template hierarchy is added (based on an example
from Marinus Schraal).

Closes: #257, #386

This should help distros update to the new version even if they have
to still support Python 2.

If there are any open questions please add something in #392

Fixes #392

This is a leftover from when things were split up

Less macro magic

Less macro magic

In gtk!1134 the method was changed to a constructor
which means the API is different between older and newer gtk.

Add fallbacks for both in our overrides so both ways work all the time.

It has been removed (gtk commit
4dd780a96b1d37903ab88a4ae4536329cd9e164e)

The associated tests are updated or skipped for Gtk 4.

It has been removed (gtk commit
44e153d8a8679633681dd3ae2029735255e4f839).

The associated test is removed.

This no longer works since pytest 5.4.0. Somehow the xfail gets checked before
the plugin runs so errors thrown in the plugin get ignored.

Depend on setuptools to make sure we write out requires-python in all cases

Some packages have started failing to install with the pip shipped
with xenial.

It still supports Python 2

master has dropped Python 2 support

These API's have been removed (gtk commit 7ee5779efcf5).

This issue was introduced in a102f046.

Signed-off-by: Dan Yeaw <dan@yeaw.me>

More packages are required to be able to run the example on the getting started page on openSUSE