Require Python 3.9 and run tests with Python 3.9

PiperOrigin-RevId: 597164695

.github/workflows/build.yaml

@@ -15,7 +15,7 @@ jobs:
     - name: Set up Python
       uses: actions/setup-python@v2
       with:
-        python-version: '3.8.x'
+        python-version: '3.9'
     - name: Install dependencies
       run: pip install -e .[cache-tasks,test]
     - name: Test with pytest

seqio/version.py

@@ -18,4 +18,4 @@
 pulling in all the dependencies in __init__.py.
 """
 
-__version__ = '0.0.17'
+__version__ = '0.0.18'

setup.py

@@ -61,6 +61,7 @@
         # sentencepiece package.
         'protobuf<=3.20.3',
     ],
+    requires_python='>=3.9',
     extras_require={
         'gcp': [
             'gevent',