Add python version to github PR action

Author: soimkim

.github/workflows/pull-request.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.6]
+        python-version: [3.6, 3.7]
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python ${{ matrix.python-version }}

tox.ini

@@ -6,7 +6,6 @@ skipdist = true
 
 [testenv]
 install_command = pip install {opts} {packages}
-basepython= python3.6
 whitelist_externals = cat
 setenv =
   PYTHONPATH=.