tox: enable python 3.10 testing

Note that in YAML, Python version 3.10 would be parsed as 3.1,
hence I put all the Python versions in quotes.
More on this:
https://github.com/actions/setup-python/issues/160

Signed-off-by: Daniel Kutik <daniel.kutik@lavawerk.com>
Change-Id: Iba380a6a6a6de8486486c8981e712c7bf4dfe759
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/353019
Reviewed-by: Mike Frysinger <vapier@google.com>
diff --git a/.github/workflows/test-ci.yml b/.github/workflows/test-ci.yml
index 1988185..ff03eb2 100644
--- a/.github/workflows/test-ci.yml
+++ b/.github/workflows/test-ci.yml
@@ -14,7 +14,7 @@
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        python-version: [3.6, 3.7, 3.8, 3.9]
+        python-version: ['3.6', '3.7', '3.8', '3.9', '3.10']
     runs-on: ${{ matrix.os }}
 
     steps:
diff --git a/tox.ini b/tox.ini
index aa4e297..1d072f6 100644
--- a/tox.ini
+++ b/tox.ini
@@ -15,7 +15,7 @@
 # https://tox.readthedocs.io/
 
 [tox]
-envlist = py36, py37, py38, py39
+envlist = py36, py37, py38, py39, py310
 
 [gh-actions]
 python =
@@ -23,6 +23,7 @@
     3.7: py37
     3.8: py38
     3.9: py39
+    3.10: py310
 
 [testenv]
 deps = pytest