CI Py3.10.

.github/workflows/build.yml

@@ -7,7 +7,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-18.04, macos-10.15, windows-2019]
-        python-version: ["3.7", "3.8", "3.9"]
+        python-version: ["3.7", "3.8", "3.9", "3.10"]
       fail-fast: false
     runs-on: ${{ matrix.os }}
     steps:
@@ -53,9 +53,8 @@ jobs:
 
         python -mpip install dist/*.whl &&
         python tools/ensure-mpl-test-data.py &&
-        # pytest 6.2 is incompatible with matplotlib<3.4
         # pytest-{instafail,timeout} useful for hanging tests.
-        python -mpip install 'pytest<6.2' pytest-instafail pytest-timeout
+        python -mpip install pytest pytest-instafail pytest-timeout
     - name: Test
       shell: bash
       run: |

run-mpl-test-suite.py

@@ -7,7 +7,6 @@
 """
 
 from argparse import ArgumentParser
-from distutils.version import LooseVersion
 import os
 from pathlib import Path
 import sys
@@ -21,6 +20,8 @@
 import matplotlib.backends.backend_agg
 import matplotlib.testing.decorators
 
+from packaging.version import parse as parse_version
+
 import pytest
 
 
@@ -194,7 +195,7 @@ def pytest_collection_modifyitems(session, config, items):
         ]
         for nodeid in nodeids
     }
-    if LooseVersion(mpl.__version__) < "3.0":
+    if parse_version(mpl.__version__) < parse_version("3.0"):
         module_markers.update({
             "matplotlib.sphinxext.test_tinypages": irrelevant,  # matplotlib#11360.
         })