python: upgrade to 3.9 (#131)

3.7 and 3.8 are both EOL

commit-id:287d3a4d

Author: dhalperi

.github/workflows/reusable-precommit.yml

@@ -153,7 +153,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          python-version: 3.7
+          python-version: 3.9
       - name: Build wheel
         run: |
           cd pybatfish

tests/test_batfish_container.sh

@@ -9,7 +9,7 @@ bash conda.sh -b -p $HOME/miniconda
 export PATH="$HOME/miniconda/bin:$PATH"
 # pip 20.3 has problems resolving dependencies correctly, so pin to last working version
 # See related resolver issue: https://github.com/pypa/pip/issues/9187
-conda create -y -n conda_env python=3.7 pip=20.2.4
+conda create -y -n conda_env python=3.9 pip=20.2.4
 source activate conda_env
 
 # Install specific version of Pybatfish if specified, otherwise use the available version/wheel artifacts