Issue #22168: Prevent turtle AttributeError with non-default Canvas on OS X.

--HG--
branch : 3.4
Fixed re tests incorrectly ported from 2.x to 3.x.

--HG--
branch : 3.4
Use more appropriate asserts in re tests.

--HG--
branch : 3.4
Issue #22384: An exception in Tkinter callback no longer crashes the program
when it is run with pythonw.exe.

Documented that Tk.report_callback_exception() is purposed to be overriden in
applications.

--HG--
branch : 3.4