doc: fix pylint errors

doc/docgen.py

@@ -487,7 +487,8 @@ class AutogenDoc():
             f'autogen_{name}.{self.locale[:2]}.adoc',
         )
         self.filename_tmp = f'{self.filename}.tmp'
-        self._file = open(self.filename_tmp, 'w')
+        # pylint: disable=consider-using-with
+        self._file = open(self.filename_tmp, 'w', encoding='utf-8')
 
     def write_autogen_files(self, weechat_doc):
         """Write auto-generated files."""

doc/python_stub.py

@@ -56,7 +56,8 @@ def print_stub_constants() -> None:
         "string": "str",
     }
     constant_pattern = re.compile(CONSTANT_RE)
-    with open(DOC_DIR / "weechat_scripting.en.adoc") as scripting_file:
+    with open(DOC_DIR / "weechat_scripting.en.adoc",
+              encoding="utf-8") as scripting_file:
         scripting = scripting_file.read()
         for match in constant_pattern.finditer(scripting):
             print(f'{match["constant"]}: {types[match["type"]]}')
@@ -65,7 +66,8 @@ def print_stub_constants() -> None:
 def print_stub_functions() -> None:
     """Print function prototypes, extracted from the Plugin API reference."""
     function_pattern = re.compile(FUNCTION_RE, re.DOTALL)
-    with open(DOC_DIR / "weechat_plugin_api.en.adoc") as api_doc_file:
+    with open(DOC_DIR / "weechat_plugin_api.en.adoc",
+              encoding="utf-8") as api_doc_file:
         api_doc = api_doc_file.read()
         for match in function_pattern.finditer(api_doc):
             url = f'https://weechat.org/doc/api/#_{match["function"]}'