Add workflow to run flake8

.flake8

@@ -0,0 +1,4 @@
+[flake8]
+max-line-length = 120
+exclude = tests/*
+ignore = E501, E722, W391, F821

.github/workflows/flake8.yml

@@ -0,0 +1,19 @@
+name: flake8
+
+on:
+  pull_request: {}
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+    - name: Run flake8 with tox
+      run: |
+        pip install tox
+        tox -e flake8

pyproject.toml

@@ -29,4 +29,4 @@ dependencies = [
 postgres = ["psycopg2", "db-dtypes"]
 bigquery = ["google-auth", "google-cloud-bigquery"]
 snowflake = ["snowflake-connector-python"]
-test = ["tox"]
+test = ["tox", "pytest"]