[hacking] N373 do not use eventlet primitives

Add a new hacking check to prevent adding Eventlet concurrency
primitives where the stdlib one is equivalent.

Right now only eventlet/greenthread.sleep is checked but as we progress
with the transformation we will add more primitives.

Change-Id: I1310bb7a8c8133364060eb8814226cab52219171

HACKING.rst

@@ -77,6 +77,8 @@ Nova Specific Commandments
 - [N370] Don't use or import six
 - [N371] You must explicitly import python's mock: ``from unittest import mock``
 - [N372] Don't use the setDaemon method. Use the daemon attribute instead.
+- [N373] Don't use eventlet specific concurrency primitives. Use the one
+  from stdlib instead. E.g. eventlet.sleep => time.sleep
 
 Creating Unit Tests
 -------------------

nova/hacking/checks.py

@@ -143,6 +143,8 @@ rwlock_re = re.compile(
 six_re = re.compile(r"^(import six(\..*)?|from six(\..*)? import .*)$")
 # Regex for catching the setDaemon method
 set_daemon_re = re.compile(r"\.setDaemon\(")
+eventlet_stdlib_primitives_re = re.compile(
+    r".*(eventlet|greenthread)\.sleep\(.*")
 
 
 class BaseASTChecker(ast.NodeVisitor):
@@ -1099,3 +1101,20 @@ def check_set_daemon(logical_line):
     if res:
         yield (0, "N372: Don't use the setDaemon method. "
                   "Use the daemon attribute instead.")
+
+
+@core.flake8ext
+def check_eventlet_primitives(logical_line, filename):
+    """Check for use of any eventlet primitives where the stdlib equivalent
+    should be used
+
+    N373
+    """
+    msg = (
+        "N373: Use the stdlib concurrency primitive instead of the Eventelt "
+        "specific one")
+
+    match = re.match(eventlet_stdlib_primitives_re, logical_line)
+
+    if match:
+        yield (0, msg)

nova/tests/unit/test_hacking.py

@@ -1064,3 +1064,20 @@ class HackingTestCase(test.NoDBTestCase):
                    self.thread.setdaemon(True)
                """
         self._assert_has_no_errors(code, checks.check_set_daemon)
+
+    def test_check_eventlet_primitives(self):
+        code = """
+                    eventlet.sleep(0)
+                    eventlet.sleep(1)
+                    greenthread.sleep(0)
+                    greenthread.sleep(1)
+               """
+        errors = [(x + 1, 0, 'N373') for x in range(4)]
+        self._assert_has_errors(
+            code, checks.check_eventlet_primitives, expected_errors=errors)
+
+        code = """
+                    time.sleep(0)
+                    time.sleep(1)
+               """
+        self._assert_has_no_errors(code, checks.check_eventlet_primitives)

tox.ini

@@ -358,6 +358,7 @@ extension =
   N370 = checks:check_six
   N371 = checks:import_stock_mock
   N372 = checks:check_set_daemon
+  N373 = checks:check_eventlet_primitives
 paths =
   ./nova/hacking