Make test_revoke_cert_project_not_found_chdir_fails deterministic

Commit b64cebe2eb removed the mock on
os.chdir to always fail with OSError in the test.

The revoke_cert method is using the ca_folder method to get the path and
that checks CONF.use_project_ca which is by default False, so the
project_id isn't even used in the path we're changing to before running
the command, it just uses the global static CONF.ca_path.  If that path
exists when this test runs, os.chdir won't raise OSError and the
assertion in the test will fail.

This change makes the test deterministic by (1) setting
use_project_ca=True and (2) using a random project_id uuid.

Closes-Bug: #1495547

Change-Id: I0dc6574b6644aa09028a07503a3d0b82e68e69d2

nova/tests/unit/test_crypto.py

@@ -17,6 +17,7 @@ Tests for Crypto module.
 """
 
 import os
+import uuid
 
 from cryptography.hazmat import backends
 from cryptography.hazmat.primitives import serialization
@@ -164,8 +165,9 @@ class RevokeCertsTest(test.TestCase):
                           2, 'test_file')
 
     def test_revoke_cert_project_not_found_chdir_fails(self, *args, **kargs):
+        self.flags(use_project_ca=True)
         self.assertRaises(exception.ProjectNotFound, crypto.revoke_cert,
-                          2, 'test_file')
+                          str(uuid.uuid4()), 'test_file')
 
 
 class CertExceptionTests(test.TestCase):