gh-140502: fix default REPL does not handle tab right

[yihong0618]

and found there is no test for disp_str
also add a test for it.

after this patch
cc @sergey-miryanov

• Issue: Python3.15.0a1 REPL : issue with pasting of Tab indented multiline code #140502

[sergey-miryanov]

On windows it works as expected without patch.
On ubuntu 24.10 in WSL (default terminal) before patch:

Python 3.15.0a1+ (heads/main:c6d4c79c9ab, Oct 29 2025, 00:24:08) [GCC 14.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from PyQt6.QtWidgets import QApplication, QWidget
... from PyQt6.QtGui import QPainter, QColor, QPen
... from PyQt6.QtCore import Qt, QRect
... from cv2 import (
...     cvtColor                                                        ,
                                                    ...                 COLOR_Lab2RGB                           ,
                                                                                         ...            COLOR_HSV2RGB_FULL                      ,
                                                                                                                     ...                COLOR_HLS2RGB_FULL                      ,
                                                                                                                                                     ... 
                                                                                                                                                     ...                COLOR_RGB2Lab                           ,
                                                                                                                                                                                         ...            COLOR_RGB2HSV_FULL                      ,
                                                                                                                                                                                                                     ...                COLOR_RGB2HLS_FULL                      ,
                                                                                                                                                                                                                                                     ... 
                                                                                                                                                                                                                                                     ... )
                                                                                                                                                                                                                                                     ... 
Traceback (most recent call last):
  File "<python-input-0>", line 1, in <module>
    from PyQt6.QtWidgets import QApplication, QWidget
ModuleNotFoundError: No module named 'PyQt6'
>>> exit()

After patch:

Python 3.15.0a1+ (heads/main:c6d4c79c9ab, Oct 29 2025, 00:24:08) [GCC 14.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from PyQt6.QtWidgets import QApplication, QWidget
... from PyQt6.QtGui import QPainter, QColor, QPen
... from PyQt6.QtCore import Qt, QRect
... from cv2 import (
...         cvtColor                                                        ,
...                 COLOR_Lab2RGB                           ,
...                 COLOR_HSV2RGB_FULL                      ,
...                 COLOR_HLS2RGB_FULL                      ,
... 
...                 COLOR_RGB2Lab                           ,
...                 COLOR_RGB2HSV_FULL                      ,
...                 COLOR_RGB2HLS_FULL                      ,
... 
... )
... 
Traceback (most recent call last):
  File "<python-input-0>", line 1, in <module>
    from PyQt6.QtWidgets import QApplication, QWidget
ModuleNotFoundError: No module named 'PyQt6'

So, it seems working.

[sergey-miryanov]

Would it be better to use a constant here?

[yihong0618]

I think the code below not use constant, so its fine here

[sergey-miryanov]

@pablogsal @ambv Could you please take a look.