chore(python): add nox session to sort python imports (#567)

Source-Link: googleapis/synthtool@1b71c10
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:00c9d764fd1cd56265f12a5ef4b99a0c9e87cf261018099141e2ca5158890416

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: gcf-owl-bot[bot]

.github/.OwlBot.lock.yaml

@@ -13,5 +13,5 @@
 # limitations under the License.
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-python:latest
-  digest: sha256:8a5d3f6a2e43ed8293f34e06a2f56931d1e88a2694c3bb11b15df4eb256ad163
-# created: 2022-04-06T10:30:21.687684602Z
+  digest: sha256:00c9d764fd1cd56265f12a5ef4b99a0c9e87cf261018099141e2ca5158890416
+# created: 2022-04-20T23:42:53.970438194Z

noxfile.py

@@ -26,7 +26,8 @@
 
 PYTYPE_VERSION = "pytype==2020.7.24"
 BLACK_VERSION = "black==22.3.0"
-BLACK_PATHS = ["docs", "google", "tests", "noxfile.py", "setup.py"]
+ISORT_VERSION = "isort==5.10.1"
+LINT_PATHS = ["docs", "google", "tests", "noxfile.py", "setup.py"]
 
 DEFAULT_PYTHON_VERSION = "3.8"
 
@@ -90,7 +91,7 @@ def lint(session):
     session.run(
         "black",
         "--check",
-        *BLACK_PATHS,
+        *LINT_PATHS,
     )
     session.run("flake8", "google", "tests")
 
@@ -101,7 +102,27 @@ def blacken(session):
     session.install(BLACK_VERSION)
     session.run(
         "black",
-        *BLACK_PATHS,
+        *LINT_PATHS,
+    )
+
+
+@nox.session(python=DEFAULT_PYTHON_VERSION)
+def format(session):
+    """
+    Run isort to sort imports. Then run black
+    to format code to uniform standard.
+    """
+    session.install(BLACK_VERSION, ISORT_VERSION)
+    # Use the --fss option to sort imports using strict alphabetical order.
+    # See https://pycqa.github.io/isort/docs/configuration/options.html#force-sort-within-sections
+    session.run(
+        "isort",
+        "--fss",
+        *LINT_PATHS,
+    )
+    session.run(
+        "black",
+        *LINT_PATHS,
     )