DOC: Fix encoding of docstring validation for Windows

scripts/tests/test_validate_docstrings.py

@@ -1052,6 +1052,12 @@ def test_raises_for_invalid_attribute_name(self, invalid_name):
         with pytest.raises(AttributeError, match=msg):
             validate_docstrings.Docstring(invalid_name)
 
+    @pytest.mark.parametrize('name', [
+        'pandas.Series.str.isdecimal', 'pandas.Series.str.islower'])
+    def test_encode_content_write_to_file(self, name):  # GH25466
+        docstr = validate_docstrings.Docstring(name).validate_pep8()
+        assert len(list(docstr)) == 0
+
 
 class TestMainFunction:
     def test_exit_status_for_validate_one(self, monkeypatch):

scripts/validate_docstrings.py

@@ -580,7 +580,7 @@ def validate_pep8(self):
         application = flake8.main.application.Application()
         application.initialize(["--quiet"])
 
-        with tempfile.NamedTemporaryFile(mode='w') as file:
+        with tempfile.NamedTemporaryFile(mode='w', encoding='utf-8') as file:
             file.write(content)
             file.flush()
             application.run_checks([file.name])