Support Python 3.9 (#3848)

.github/workflows/build.yml

@@ -43,7 +43,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [ 3.6, 3.7, 3.8 ]
+        python-version: [ 3.6, 3.7, 3.8, 3.9 ]
 
     steps:
       - uses: actions/checkout@v2
@@ -112,7 +112,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [3.6, 3.7, 3.8]
+        python-version: [3.6, 3.7, 3.8, 3.9]
 
     steps:
     - uses: actions/checkout@v2
@@ -157,7 +157,7 @@ jobs:
     needs: lint
     strategy:
       matrix:
-        python-version: [3.6, 3.7, 3.8]
+        python-version: [3.6, 3.7, 3.8, 3.9]
 
     steps:
     - uses: actions/checkout@v2

codecov.yml

@@ -1,7 +1,7 @@
 codecov:
   notify:
     # Leave a GitHub comment after all builds have passed
-    after_n_builds: 6
+    after_n_builds: 8
 coverage:
   status:
     project:

setup.py

@@ -129,6 +129,7 @@ setup(
         "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.9",
         "License :: OSI Approved :: Apache Software License",
         "Topic :: Software Development :: Testing",
     ],