Enable the PLW1514 lint in Ruff

.ruff.toml

@@ -57,7 +57,6 @@ ignore = [
     "PLR6201",  # Use a set literal when testing for membership
     "PLR6301",  # Method `{method_name}` could be a function, class method, or static method
     # pylint ('PLW')
-    "PLW1514",  # `{function_name}` in text mode without explicit `encoding` argument
     "PLW1641",  # Object does not implement `__hash__` method
     "PLW2901",  # Outer {outer_kind} variable `{name}` overwritten by inner {inner_kind} target
     "PLW3201",  # Dunder method `{name}` has no special meaning in Python 3

sphinx/cmd/make_mode.py

@@ -106,7 +106,7 @@ class Make:
         try:
             with chdir(self.build_dir_join('latex')):
                 if '-Q' in self.opts:
-                    with open('__LATEXSTDOUT__', 'w') as outfile:
+                    with open('__LATEXSTDOUT__', 'w', encoding='utf-8') as outfile:
                         returncode = subprocess.call(
                             [
                                 makecmd,

sphinx/util/exceptions.py

@@ -41,7 +41,7 @@ def save_traceback(app: Sphinx | None, exc: BaseException) -> str:
         )
 
     with NamedTemporaryFile(
-        'w', suffix='.log', prefix='sphinx-err-', delete=False
+        'w', encoding='utf-8', suffix='.log', prefix='sphinx-err-', delete=False
     ) as f:
         f.write(f"""\
 # Platform:         {sys.platform}; ({platform.platform()})