Lint NDB on CI (#6822)

Author: crwilcox

noxfile.py

@@ -68,19 +68,41 @@ def cover(session):
     session.run("coverage", "erase")
 
 
+def run_black(session, use_check=False):
+    args = ["black"]
+    if use_check:
+        args.append("--check")
+
+    args.extend(
+        [
+            "--line-length=79",
+            get_path("docs"),
+            get_path("noxfile.py"),
+            get_path("src"),
+            get_path("tests"),
+        ]
+    )
+
+    session.run(*args)
+
+
+@nox.session(py=DEFAULT_INTERPRETER)
+def lint(session):
+    """Run linters.
+    Returns a failure if the linters find linting errors or sufficiently
+    serious code quality issues.
+    """
+    session.install("flake8", "black")
+    run_black(session, use_check=True)
+    session.run("flake8", "google", "tests")
+
+
 @nox.session(py=DEFAULT_INTERPRETER)
 def blacken(session):
     # Install all dependencies.
     session.install("black")
     # Run ``black``.
-    session.run(
-        "black",
-        "--line-length=79",
-        get_path("docs"),
-        get_path("noxfile.py"),
-        get_path("src"),
-        get_path("tests"),
-    )
+    run_black(session)
 
 
 @nox.session(py=DEFAULT_INTERPRETER)

tests/unit/test_model.py

@@ -1370,7 +1370,7 @@ def test_compare_valid():
     def test_compare_invalid():
         prop = model.ModelKey()
         with pytest.raises(exceptions.BadValueError):
-            prop == None
+            prop == None  # noqa: E711
 
     @staticmethod
     def test__validate():

tests/unit/test_query.py

@@ -51,13 +51,13 @@ class TestParameterizedThing:
     def test___eq__():
         thing = query.ParameterizedThing()
         with pytest.raises(NotImplementedError):
-            thing == None
+            thing == unittest.mock.sentinel.other
 
     @staticmethod
     def test___ne__():
         thing = query.ParameterizedThing()
         with pytest.raises(NotImplementedError):
-            thing != None
+            thing != unittest.mock.sentinel.other
 
 
 class TestParameter:
@@ -143,12 +143,12 @@ def _make_one():
     def test___eq__(self):
         node = self._make_one()
         with pytest.raises(NotImplementedError):
-            node == None
+            node == unittest.mock.sentinel.other
 
     def test___ne__(self):
         node = self._make_one()
         with pytest.raises(NotImplementedError):
-            node != None
+            node != unittest.mock.sentinel.other
 
     def test___le__(self):
         node = self._make_one()

tests/unit/test_utils.py

@@ -17,7 +17,6 @@
 import pytest
 
 from google.cloud.ndb import utils
-import tests.unit.utils
 
 
 def test___all__():