Fix tests for python-3.10 and add 3.10 to CI matrix

This PR changed the "optional arguments" to "optional" in 3.10, breaking
some tests.

python/cpython#23858

Author: mikelolasagasti

.github/workflows/test.yml

@@ -16,7 +16,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [3.6, 3.7, 3.8, 3.9]
+        python-version: ['3.6', '3.7', '3.8', '3.9', '3.10']
         os: [ubuntu-latest]
     env:
       PYTHON: ${{ matrix.python-version }}

sphinxarg/parser.py

@@ -154,7 +154,9 @@ def parse_parser(parser, data=None, **kwargs):
             continue
 
         # Upper case "Positional Arguments" and "Optional Arguments" titles
-        if action_group.title == 'optional arguments':
+        # Since python-3.10 'optional arguments' changed to 'options'
+        # more info: https://github.com/python/cpython/pull/23858
+        if action_group.title == 'optional arguments' or action_group.title == 'options':
             action_group.title = 'Named Arguments'
         if action_group.title == 'positional arguments':
             action_group.title = 'Positional Arguments'