Make most test cases work on MacOS

When developing on MacOS currently running test cases is only possible
via remote execution on a linux box. With latest master version of
gear it is possible to run zuul test cases also natively on MacOS with
minimal modification. Since bwrap is not available on mac add a small
fake bwrap script that can be linked into the PATH to make test cases
work that use ansible.

Change-Id: I02d7cc30b872c7406cf6641762e1f7b89e99479d

tests/base.py

@@ -62,6 +62,7 @@ from git.exc import NoSuchPathError
 import yaml
 import paramiko
 from zuul.lib.connections import ConnectionRegistry
+from psutil import Popen
 
 import tests.fakegithub
 import zuul.driver.gerrit.gerritsource as gerritsource
@@ -3310,6 +3311,18 @@ class PostgresqlSchemaFixture(fixtures.Fixture):
         cur.execute("drop user %s" % self.name)
 
 
+class FakeCPUTimes:
+    def __init__(self):
+        self.user = 0
+        self.system = 0
+        self.children_user = 0
+        self.children_system = 0
+
+
+def cpu_times(self):
+    return FakeCPUTimes()
+
+
 class BaseTestCase(testtools.TestCase):
     log = logging.getLogger("zuul.test")
     wait_timeout = 90
@@ -3408,6 +3421,10 @@ class BaseTestCase(testtools.TestCase):
         self.addCleanup(handler.close)
         self.addCleanup(handler.flush)
 
+        if sys.platform == 'darwin':
+            # Popen.cpu_times() is broken on darwin so patch it with a fake.
+            Popen.cpu_times = cpu_times
+
 
 class SymLink(object):
     def __init__(self, target):

tests/unit/test_bubblewrap.py

@@ -13,6 +13,7 @@
 import fixtures
 import logging
 import subprocess
+import sys
 import tempfile
 import testtools
 import time
@@ -21,6 +22,7 @@ import os
 from zuul.driver import bubblewrap
 from zuul.executor.server import SshAgent
 from tests.base import iterate_timeout
+from unittest import skipIf
 
 
 class TestBubblewrap(testtools.TestCase):
@@ -53,6 +55,7 @@ class TestBubblewrap(testtools.TestCase):
         # Make sure the _r's are closed
         self.assertEqual([], po.fds)
 
+    @skipIf(sys.platform == 'darwin', 'Not supported on MacOS')
     def test_bubblewrap_leak(self):
         bwrap = bubblewrap.BubblewrapDriver()
         context = bwrap.getExecutionContext()

tools/fake_bwrap.py

@@ -0,0 +1,80 @@
+#!/usr/bin/env python3
+
+# Copyright 2020 BMW Group
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import argparse
+import os
+import subprocess
+
+
+def main():
+    pos_args = {
+        '--dir': 1,
+        '--tmpfs': 1,
+        '--ro-bind': 2,
+        '--bind': 2,
+        '--chdir': 1,
+        '--uid': 1,
+        '--gid': 1,
+        '--file': 2,
+        '--proc': 1,
+        '--dev': 1,
+    }
+    bool_args = [
+        '--unshare-all',
+        '--unshare-user',
+        '--unshare-user-try',
+        '--unshare-ipc',
+        '--unshare-pid',
+        '--unshare-net',
+        '--unshare-uts',
+        '--unshare-cgroup',
+        '--unshare-cgroup-try',
+        '--share-net',
+        '--die-with-parent',
+    ]
+    parser = argparse.ArgumentParser()
+    for arg, nargs in pos_args.items():
+        parser.add_argument(arg, nargs=nargs, action='append')
+    for arg in bool_args:
+        parser.add_argument(arg, action='store_true')
+    parser.add_argument('args', metavar='args', nargs=argparse.REMAINDER,
+                        help='Command')
+
+    args = parser.parse_args()
+
+    for fd, path in args.file:
+        fd = int(fd)
+        if path.startswith('/etc'):
+            # Ignore write requests to /etc
+            continue
+        print('Writing file from %s to %s' % (fd, path))
+        count = 0
+        with open(path, 'wb') as output:
+            data = os.read(fd, 32000)
+            while data:
+                count += len(data)
+                output.write(data)
+                data = os.read(fd, 32000)
+        print('Wrote file (%s bytes)' % count)
+
+    if args.chdir:
+        os.chdir(args.chdir[0][0])
+    result = subprocess.run(args.args, shell=False, check=False)
+    exit(result.returncode)
+
+
+if __name__ == '__main__':
+    main()