Resolve EncodingWarning in tests

Author: AA-Turner

tests/conftest.py

@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+import sys
+import warnings
 from pathlib import Path
 
 import pytest
@@ -13,6 +15,14 @@
 else:
     mpl.rcParams['figure.max_open_warning'] = 0
 
+if sys.version_info[:2] >= (3, 10):
+    warnings.filterwarnings(
+        'ignore',
+        category=EncodingWarning,  # NoQA: F821
+        module='matplotlib.font_manager',
+    )
+
+
 pytest_plugins = ['sphinx.testing.fixtures']
 
 
@@ -34,9 +44,9 @@ def content(app):
 
 def _meta_tags(content, subdir=None):
     if subdir is None:
-        c = (content.outdir / 'index.html').read_text()
+        c = (content.outdir / 'index.html').read_text(encoding='utf-8')
     else:
-        c = (content.outdir / subdir / 'index.html').read_text()
+        c = (content.outdir / subdir / 'index.html').read_text(encoding='utf-8')
     return BeautifulSoup(c, 'html.parser').find_all('meta')