Here's a completely re-written patch!

The patch is against current 3.3 (changeset 360976a6d8b9), since that's what Terry requested recently on issue3068. It also applies cleanly to the current default branch (changeset 360976a6d8b9).

This patch has cleaner, modern code, with doc-strings everywhere and informative comments where appropriate. It also uses "import tkinter as tk" as Terry recently requested on issue3068.

Furthermore, I've added a very complete set of tests for the new extension, which tests everything I could think of and achieves 100% coverage (!) of Squeezer.py. These are modern tests which make extensive use of mocking via the awesome unittest.mock module. I've included extensive in-code comments with the tests. Hopefully these will be useful as a reference for writing additional tests for IDLE code (at least other extensions).

Finally, this patch includes a minor change to ToolTip.py, adding the ability to specify the delay after which a tooltip is displayed (was hard-coded to 1.5 seconds). This change is required by the extension (I prefer that it uses tooltips with no delay).