Update python to 3.9

Author: Sholofly

Diff for: .github/workflows/build-on-pr.yml

@@ -10,10 +10,10 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
     - uses: actions/checkout@master
-    - name: Set up Python 3.8
+    - name: Set up Python 3.9
       uses: actions/setup-python@v1
       with:
-        python-version: 3.8
+        python-version: 3.9
     - name: Install pypa/build
       run: >-
         python -m

Diff for: setup.py

@@ -32,9 +32,7 @@ def read(*parts):
         "Operating System :: OS Independent",
         "Natural Language :: English",
         "Intended Audience :: Developers",
-        "Programming Language :: Python :: 3.6",
-        "Programming Language :: Python :: 3.7",
-        "Programming Language :: Python :: 3",
+        "Programming Language :: Python :: 3.9",
         "Topic :: Software Development :: Libraries :: Python Modules",
     ],
     python_requires='>=3.8',