Add _FATAL_EXCEPTION_FORMAT_ERRORS global.

Add a new global variable to control when exception format errors
are fatal.

Also, updates the Oslo test base class to enable fatal exception
format errors.

The motivation for this change is to give projects that use
openstack common a hook to enable exception format checking when
testing.

Change-Id: Id8f4a0946b1614c8e987976b79069532a2e8608f

3 files changed, 18 insertions, 4 deletions

diff --git a/openstack/common/exception.py b/openstack/common/exception.py
index fa06d6a..4a7c72b 100644
--- a/openstack/common/exception.py
+++ b/openstack/common/exception.py
@@ -23,6 +23,8 @@ import logging
 
 from openstack.common.gettextutils import _
 
+_FATAL_EXCEPTION_FORMAT_ERRORS = False
+
 
 class Error(Exception):
     def __init__(self, message=None):
@@ -121,9 +123,12 @@ class OpenstackException(Exception):
         try:
             self._error_string = self.message % kwargs
 
-        except Exception:
-            # at least get the core message out if something happened
-            self._error_string = self.message
+        except Exception as e:
+            if _FATAL_EXCEPTION_FORMAT_ERRORS:
+                raise e
+            else:
+                # at least get the core message out if something happened
+                self._error_string = self.message
 
     def __str__(self):
         return self._error_string
diff --git a/tests/unit/test_exception.py b/tests/unit/test_exception.py
index c03a41d..6fe93ac 100644
--- a/tests/unit/test_exception.py
+++ b/tests/unit/test_exception.py
@@ -88,7 +88,8 @@ class OpenstackExceptionTest(utils.BaseTestCase):
         err = self.TestException(test=test_message)
         self.assertEqual(err._error_string, test_message)
 
-    def test_error_forating_error_string(self):
+    def test_error_formating_error_string(self):
+        self.stubs.Set(exception, '_FATAL_EXCEPTION_FORMAT_ERRORS', False)
         err = self.TestException(lol='U mad brah')
         self.assertEqual(err._error_string, self.TestException.message)
 
diff --git a/tests/utils.py b/tests/utils.py
index f9854ca..2d681ae 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -24,6 +24,7 @@ import testtools
 
 from openstack.common import cfg
 from openstack.common.fixture import moxstubout
+from openstack.common import exception
 
 CONF = cfg.CONF
 
@@ -36,6 +37,13 @@ class BaseTestCase(testtools.TestCase):
         self.addCleanup(CONF.reset)
         self.useFixture(fixtures.FakeLogger('openstack.common'))
         self.useFixture(fixtures.Timeout(30, True))
+        self.stubs.Set(exception, '_FATAL_EXCEPTION_FORMAT_ERRORS', True)
+
+    def tearDown(self):
+        super(BaseTestCase, self).tearDown()
+        CONF.reset()
+        self.stubs.UnsetAll()
+        self.stubs.SmartUnsetAll()
 
     def config(self, **kw):
         """