idle cannot save file with non ascii character, leading to:

Exception in Tkinter callback
Traceback (most recent call last):
  File "/usr/lib64/python3.8/tkinter/__init__.py", line 1883, in __call__
    return self.func(*args)
  File "/usr/lib64/python3.8/idlelib/multicall.py", line 176, in handler
    r = l[i](event)
  File "/usr/lib64/python3.8/idlelib/iomenu.py", line 199, in save
    else:
  File "/usr/lib64/python3.8/idlelib/iomenu.py", line 232, in writefile
    text = self.fixnewlines()
  File "/usr/lib64/python3.8/idlelib/iomenu.py", line 271, in encode
    encoded = chars.encode('ascii', 'replace')
NameError: name 'io' is not defined

just adding `import io` seems to fix this.

Your suggestion is correct.

A side issue is that the line numbers in the traceback are correct but the quoted text lines from iomenu (and only iomenu) are wrong, being from the line previous.  I will have to investigate this discrepancy.

After the patch, two weeks ago, for #41158, iomenu line 199 in save is
            if self.writefile(self.filename):
line 232 in writefile is 
        chars = self.encode(text)
line 291 in encode is
        enc, _ = tokenize.detect_encoding(io.BytesIO(encoded).readline)
This is only tried if ascii encoding fails and require the addition of 'import io'.

Before I close this, I will try to add a unittest that similarly fails without the import added, as well as some others for other exit points.

Łukasz, please pull this simple fix to a 3.9.0b4 and 3.8.4 regression into 3.8.5.  It disabled saving files with non-ascii chars.

New changeset 38d3864efe914fda64553e2ec75c9ec15574483f by Terry Jan Reedy in branch 'master':
 bpo-41300: IDLE - save files with non-ascii chars  (GH-21512)
https://github.com/python/cpython/commit/38d3864efe914fda64553e2ec75c9ec15574483f

New changeset 5a7aa280457423b97512810d6d9baac37f99fbf4 by Miss Islington (bot) in branch '3.9':
bpo-41300: IDLE - save files with non-ascii chars  (GH-21512)
https://github.com/python/cpython/commit/5a7aa280457423b97512810d6d9baac37f99fbf4

New changeset ffeb9202540c07d384f82ff3ab86c37c1433283a by Miss Islington (bot) in branch '3.8':
[3.8] bpo-41300: IDLE - save files with non-ascii chars  (GH-21512)
https://github.com/python/cpython/commit/ffeb9202540c07d384f82ff3ab86c37c1433283a

Łukasz, Please cherry-pick the 3.8 backport,  ffeb920, as it has a 3.8-specific fixup to idlelib/NEWS.txt.

I verified the bug and fix on Windows.  I am leaving this open to add automated tests.

Problem also reported on #41319

#41319 should be closed as a duplicate, but site will not currently allow me to do so.

Released.

The fix is in both 3.8.5 and 3.9.0b5, both released today.
"print('eyes ∢∢ snake 🐍')", for instance, in the editor, can be saved and run.  (Note that astral chars like the snake disrupt editing a bit, but once there, can be saved and will print.

Łukasz, thanks for getting this in.  I am leaving this open to add tests, but will remove you as nosy.

#41373 is about another issue with the new iomenu code.  I will close this and add tests there.