gh-127060: Disable traceback colors in IDLE

Set TERM environment variable to "dumb" to disable traceback colors
in IDLE, since IDLE doesn't understand ANSI escape sequences.

Author: vstinner

Lib/idlelib/pyshell.py

@@ -1596,6 +1596,9 @@ def main():
     enable_edit = enable_edit or edit_start
     enable_shell = enable_shell or not enable_edit
 
+    # gh-127060: Disable traceback colors
+    os.environ['TERM'] = 'dumb'
+
     # Setup root.  Don't break user code run in IDLE process.
     # Don't change environment when testing.
     if use_subprocess and not testing:

Misc/NEWS.d/next/Library/2024-12-17-13-21-52.gh-issue-127060.mv2bX6.rst

@@ -0,0 +1,2 @@
+Set TERM environment variable to "dumb" to disable traceback colors in IDLE,
+since IDLE doesn't understand ANSI escape sequences. Patch by Victor Stinner.