fix unicode err

tests/test_io.py

@@ -1,7 +1,7 @@
 import os
 import unittest
 from pathlib import Path
-from unittest.mock import patch, MagicMock
+from unittest.mock import MagicMock, patch
 
 from aider.io import AutoCompleter, InputOutput
 from aider.utils import ChdirTemporaryDirectory
@@ -43,23 +43,20 @@ class TestInputOutput(unittest.TestCase):
             autocompleter = AutoCompleter(root, rel_fnames, addable_rel_fnames, commands, "utf-8")
             self.assertEqual(autocompleter.words, set(rel_fnames))
 
-    @patch('aider.io.PromptSession')
+    @patch("aider.io.PromptSession")
     def test_get_input_is_a_directory_error(self, MockPromptSession):
-        # Set the environment variable to ensure UTF-8 encoding
-        os.environ["PYTHONIOENCODING"] = "utf-8"
-
         # Mock the PromptSession to simulate user input
         mock_session = MockPromptSession.return_value
         mock_session.prompt.return_value = "test input"
 
-        io = InputOutput()
+        io = InputOutput(pretty=False)  # Windows tests throw UnicodeDecodeError
         root = "/"
         rel_fnames = ["existing_file.txt"]
         addable_rel_fnames = ["new_file.txt"]
         commands = MagicMock()
 
         # Simulate IsADirectoryError
-        with patch('aider.io.open', side_effect=IsADirectoryError):
+        with patch("aider.io.open", side_effect=IsADirectoryError):
             result = io.get_input(root, rel_fnames, addable_rel_fnames, commands)
             self.assertEqual(result, "test input")