Issue 33855: IDLE: Minimally test every non-startup module.

For module in idlelib modules:
    Create test_module from new template.py.
    Add 'module' to docstring and import.
    Check other minimal imports.
    Create instance of each class, with requires('gui') if needed.
    Add initial coverage of this test.

I am also reviewing existing tests.

PR initially adds template, 1 new file, and edits 3 others.  Needs blurb.   I will add more, but will likely break this up into multiple PRs.  This should, of course, been done years ago.

Reviews welcome, non-Windows test would be good.  (Tal, what do you have?)

My main laptop is currently Windows 10, I use it for most CPython work.

I also have PCs running OSX, Ubuntu and Windows 7.

Terry, let me know what and when you'd like me to run on which OSs, and I'll get it done :)

debugger and debugger_r: tests are subminimal because instantiating classes is not trivial.
dynoption: skipped because I expect it will be replaced and deleted when I review PR to do so.
editor: I discovered, or rediscovered, a new shutdown issue, with EditorWindow.  It appeared in the new test_flist also.  This time, I discovered how to solve it with tcl after info, thanks to Cheryl using it for test_codecontext.
---
I am going to break this into 3 PRs.  The first third is done.  Having written this much, I think the new code is very unlikely to break on other OSes, so I don't think special testing is necessary before merging.

Tal, if you have a cpython clone on your OSX machine, it would be nice to have "python -m test.test_idle" (which runs gui tests) run in an updated repository at least once a week if there is anything new.

New changeset ee5ef309c7e2daef1248730145408f700732c42e by Terry Jan Reedy in branch 'master':
bpo-33855: Minimally test all IDLE modules. (GH-7689)
https://github.com/python/cpython/commit/ee5ef309c7e2daef1248730145408f700732c42e

New changeset 508568764593dca3844a51c10f1493413a51d66f by Miss Islington (bot) in branch '3.7':
bpo-33855: Minimally test all IDLE modules. (GH-7689)
https://github.com/python/cpython/commit/508568764593dca3844a51c10f1493413a51d66f

New changeset 833b3d2dcc7043be20ac19f7821552fcb21f4365 by Terry Jan Reedy in branch '3.6':
[3.6] bpo-33855: Minimally test all IDLE modules. (GH-7689) (GH-7734)
https://github.com/python/cpython/commit/833b3d2dcc7043be20ac19f7821552fcb21f4365

New changeset ea3dc8029ab6a0f1ee6a8a72f1612dea74892e08 by Terry Jan Reedy in branch 'master':
bpo-33855: More edits and new minimal tests for IDLE (GH-7761)
https://github.com/python/cpython/commit/ea3dc8029ab6a0f1ee6a8a72f1612dea74892e08

New changeset 740f1cb20a8ae6e7f6daa14f2e240664643ce757 by Miss Islington (bot) in branch '3.7':
bpo-33855: More edits and new minimal tests for IDLE (GH-7761)
https://github.com/python/cpython/commit/740f1cb20a8ae6e7f6daa14f2e240664643ce757

New changeset 684bc3d67797f2b5ca9368fe7ecc1c3093d7b694 by Miss Islington (bot) in branch '3.6':
bpo-33855: More edits and new minimal tests for IDLE (GH-7761)
https://github.com/python/cpython/commit/684bc3d67797f2b5ca9368fe7ecc1c3093d7b694

Spinoffs:
 change rstrip.RstripExtension to Rstrip
 change stackviewer.StackBrowser to accept exception

Change windows.py to window.py, in line with change of menu.  Should be safer with everything imported.

New changeset 4d92158f4c3917fc4fbfebff15224e74782abf79 by Terry Jan Reedy in branch 'master':
bpo-33855: Still more edits and minimal tests for IDLE  (GH-7784)
https://github.com/python/cpython/commit/4d92158f4c3917fc4fbfebff15224e74782abf79

New changeset cbaee6fe02d22f357c2edf4e463c240d5df22f14 by Miss Islington (bot) in branch '3.7':
bpo-33855: Still more edits and minimal tests for IDLE  (GH-7784)
https://github.com/python/cpython/commit/cbaee6fe02d22f357c2edf4e463c240d5df22f14

New changeset 90209a172c5b629f512cf292a22950285a2c3d81 by Miss Islington (bot) in branch '3.6':
bpo-33855: Still more edits and minimal tests for IDLE  (GH-7784)
https://github.com/python/cpython/commit/90209a172c5b629f512cf292a22950285a2c3d81

Still open for a patch explaining idle_test.template in README.

I opened #33904 for rstrip, #33905 for stackbrowser, #33906 for windows, and #33907 for calltips/CallTip renaming.

#33917 is about fixing and documenting template.py.