gh-111735: Skip `turtle` doctests when `_tkinter` is not available (#156417)

Doc/library/turtle.rst

diff --git a/Doc/library/turtle.rst b/Doc/library/turtle.rst
index 49099ae..5dc083c 100644
--- a/Doc/library/turtle.rst
+++ b/Doc/library/turtle.rst
@@ -8,11 +8,13 @@
 **Source code:** :source:`Lib/turtle.py`
 
 .. testsetup:: default
+   :skipif: _tkinter is None
 
    from turtle import *
    turtle = Turtle()
 
 .. testcleanup::
+   :skipif: _tkinter is None
 
    import os
    os.remove("my_drawing.ps")
@@ -510,6 +512,7 @@
    turtle is headed.  Do not change the turtle's heading.
 
    .. doctest::
+      :skipif: _tkinter is None
       :hide:
 
       >>> turtle.goto(0, 0)
@@ -852,6 +855,7 @@
    last *n* stamps.
 
    .. doctest::
+      :skipif: _tkinter is None
 
       >>> for i in range(8):
       ...     unused_stamp_id = turtle.stamp()
@@ -1409,8 +1413,11 @@
    font.  If *move* is true, the pen is moved to the bottom-right corner of the
    text.  By default, *move* is ``False``.
 
-   >>> turtle.write("Home = ", True, align="center")
-   >>> turtle.write((0,0), True)
+   .. doctest::
+      :skipif: _tkinter is None
+
+      >>> turtle.write("Home = ", True, align="center")
+      >>> turtle.write((0,0), True)
 
 
 Turtle state
@@ -1447,12 +1454,15 @@
 
    Return ``True`` if the Turtle is shown, ``False`` if it's hidden.
 
-   >>> turtle.hideturtle()
-   >>> turtle.isvisible()
-   False
-   >>> turtle.showturtle()
-   >>> turtle.isvisible()
-   True
+   .. doctest::
+      :skipif: _tkinter is None
+
+      >>> turtle.hideturtle()
+      >>> turtle.isvisible()
+      False
+      >>> turtle.showturtle()
+      >>> turtle.isvisible()
+      True
 
 
 Appearance
@@ -1983,6 +1993,9 @@
    method, one can make visible those parts of a drawing which were outside the
    canvas before.
 
+   .. doctest::
+      :skipif: _tkinter is None
+
       >>> screen.screensize()
       (400, 300)
       >>> screen.screensize(2000,1500)