Add main() to lockutils that creates temp dir for locks

This change would allow us to create one directory to store all locks
from all processes involved in testing in projects.

Here are examples on how to use this:
Heat - https://review.openstack.org/47360
Ceilometer - https://review.openstack.org/44809
(see tox.ini)

Change-Id: I9e1260e202b7d8feb9c762a879b9804ed85ccbd6

openstack/common/lockutils.py

@@ -20,6 +20,10 @@ import contextlib
 import errno
 import functools
 import os
+import shutil
+import subprocess
+import sys
+import tempfile
 import threading
 import time
 import weakref
@@ -277,3 +281,27 @@ def synchronized_with_prefix(lock_file_prefix):
     """
 
     return functools.partial(synchronized, lock_file_prefix=lock_file_prefix)
+
+
+def main(argv):
+    """Create a dir for locks and pass it to command from arguments
+
+    If you run this:
+    python -m openstack.common.lockutils python setup.py testr <etc>
+
+    a temporary directory will be created for all your locks and passed to all
+    your tests in an environment variable. The temporary dir will be deleted
+    afterwards and the return value will be preserved.
+    """
+
+    lock_dir = tempfile.mkdtemp()
+    os.environ["OSLO_LOCK_PATH"] = lock_dir
+    try:
+        ret_val = subprocess.call(argv[1:])
+    finally:
+        shutil.rmtree(lock_dir, ignore_errors=True)
+    return ret_val
+
+
+if __name__ == '__main__':
+    sys.exit(main(sys.argv))

tests/unit/test_lockutils.py

@@ -18,6 +18,7 @@ import fcntl
 import multiprocessing
 import os
 import shutil
+import sys
 import tempfile
 import threading
 
@@ -359,6 +360,17 @@ class LockutilsModuleTestCase(test.BaseTestCase):
             if os.path.exists(lock_dir):
                 shutil.rmtree(lock_dir, ignore_errors=True)
 
+    def test_main(self):
+        script = '\n'.join([
+            'import os',
+            'lock_path = os.environ.get("OSLO_LOCK_PATH")',
+            'assert lock_path is not None',
+            'assert os.path.isdir(lock_path)',
+        ])
+        argv = ['', sys.executable, '-c', script]
+        retval = lockutils.main(argv)
+        self.assertEqual(retval, 0, "Bad OSLO_LOCK_PATH has been set")
+
 
 class TestLockFixture(test.BaseTestCase):