Add a hacking check for importing mock library

We should only be using unittest.mock since we're python3-only,
so add and enable a hacking check that will catch it.

Change-Id: I64847f329ee3e1a3377a8c63df90c697d8b74c86

HACKING.rst

@@ -15,3 +15,4 @@ Below you can find a list of checks specific to this repository.
 - [N343] Production code must not import from ovn_octavia_provider.tests.*
 - [N344] Python 3: Do not use filter(lambda obj: test(obj), data). Replace it
          with [obj for obj in data if test(obj)].
+- [N347] Test code must not import mock library

ovn_octavia_provider/hacking/checks.py

@@ -42,6 +42,9 @@ tests_imports_from2 = re.compile(
     r"\bfrom[\s]+ovn_octavia_provider[\s]+import[\s]+tests\b")
 no_line_continuation_backslash_re = re.compile(r'.*(\\)\n')
 
+import_mock = re.compile(r"\bimport[\s]+mock\b")
+import_from_mock = re.compile(r"\bfrom[\s]+mock[\s]+import\b")
+
 
 @core.flake8ext
 def check_assert_called_once_with(logical_line, filename):
@@ -162,3 +165,19 @@ def check_python3_no_filter(logical_line):
 
     if filter_match.match(logical_line):
         yield(0, msg)
+
+
+@core.flake8ext
+def check_no_import_mock(logical_line, filename, noqa):
+    """N347 - Test code must not import mock library."""
+    msg = ("N347: Test code must not import mock library")
+
+    if noqa:
+        return
+
+    if 'ovn_octavia_provider/tests/' not in filename:
+        return
+
+    for regex in import_mock, import_from_mock:
+        if re.match(regex, logical_line):
+            yield(0, msg)

ovn_octavia_provider/tests/unit/hacking/test_checks.py

@@ -221,3 +221,28 @@ class HackingTestCase(base.BaseTestCase):
         self.assertLinePasses(f, "[obj for obj in data if test(obj)]")
         self.assertLinePasses(f, "filter(function, range(0,10))")
         self.assertLinePasses(f, "lambda x, y: x+y")
+
+    def test_check_no_import_mock(self):
+        pass_line = 'from unittest import mock'
+        fail_lines = ('import mock',
+                      'import mock as mock_lib',
+                      'from mock import patch')
+        self.assertEqual(
+            0, len(list(
+                checks.check_no_import_mock(
+                    pass_line,
+                    "ovn_octavia_provider/tests/test_fake.py",
+                    None))))
+        for fail_line in fail_lines:
+            self.assertEqual(
+                0, len(list(
+                    checks.check_no_import_mock(
+                        fail_line,
+                        "ovn_octavia_provider/common/utils.py",
+                        None))))
+            self.assertEqual(
+                1, len(list(
+                    checks.check_no_import_mock(
+                        fail_line,
+                        "ovn_octavia_provider/tests/test_fake.py",
+                        None))))

tox.ini

@@ -121,6 +121,7 @@ extension =
   N332 = checks:check_assertequal_for_httpcode
   N343 = checks:check_no_imports_from_tests
   N344 = checks:check_python3_no_filter
+  N347 = checks:check_no_import_mock
 paths =./ovn_octavia_provider/hacking
 
 [testenv:genconfig]