add tests for python 3.10 (#921)

This also raises pytest and flask-cors version to work with python 3.10. Changes are non invasive.

.github/workflows/test-docs.yml

@@ -36,7 +36,7 @@ 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"]
         dependencies: [normal]
         database: [sqlite]
         # Test other databases only with one version of Python (Debian buster has 3.7)
@@ -60,6 +60,9 @@ jobs:
           - python-version: 3.9
             dependencies: minimal
             database: sqlite
+          - python-version: "3.10"
+            dependencies: minimal
+            database: sqlite
 
     steps:
     - uses: actions/checkout@v2

setup.cfg

@@ -28,7 +28,7 @@ install_requires =
     debts>=0.5,<1
     email_validator>=1.0,<2
     Flask-Babel>=1.0,<3
-    Flask-Cors>=3.0,<4
+    Flask-Cors>=3.0.8,<4
     Flask-Mail>=0.9.1,<1
     Flask-Migrate>=2.5.3,<4  # Not following semantic versioning (e.g. https://github.com/miguelgrinberg/flask-migrate/commit/1af28ba273de6c88544623b8dc02dd539340294b)
     Flask-RESTful>=0.3.9,<1
@@ -50,7 +50,7 @@ dev =
     flake8>=3.7.9
     Flask-Testing>=0.8.1
     isort>=5.0.0
-    pytest>=5.4.1
+    pytest>=6.2.5
     tox>=3.14.6
     zest.releaser>=6.20.1
     psycopg2-binary>=2.9,<3