diff --git a/watcher/applier/primitives/change_nova_service_state.py b/watcher/applier/primitives/change_nova_service_state.py
index c82a828f6..ec8e673e1 100644
--- a/watcher/applier/primitives/change_nova_service_state.py
+++ b/watcher/applier/primitives/change_nova_service_state.py
@@ -63,7 +63,7 @@ class ChangeNovaServiceState(base.BasePrimitive):
     def nova_manage_service(self, state):
         if state is None:
             raise exception.IllegalArgumentException(
-                _("The target state is not defined"))
+                message=_("The target state is not defined"))
 
         keystone = kclient.KeystoneClient()
         wrapper = nclient.NovaClient(keystone.get_credentials(),
diff --git a/watcher/common/exception.py b/watcher/common/exception.py
index b31fe5b67..6df955a3c 100644
--- a/watcher/common/exception.py
+++ b/watcher/common/exception.py
@@ -220,51 +220,16 @@ class PatchError(Invalid):
 # decision engine
 
 
-class BaseException(Exception):
-
-    def __init__(self, desc=""):
-        if (not isinstance(desc, six.string_types)):
-            raise ValueError(_("Description must be an instance of str"))
-
-        desc = desc.strip()
-
-        self._desc = desc
-
-    def get_description(self):
-        return self._desc
-
-    def get_message(self):
-        return _("An exception occurred without a description")
-
-    def __str__(self):
-        return self.get_message()
+class IllegalArgumentException(WatcherException):
+    msg_fmt = _('Illegal argument')
 
 
-class IllegalArgumentException(BaseException):
-    def __init__(self, desc):
-        desc = desc or _("Description cannot be empty")
-        super(IllegalArgumentException, self).__init__(desc)
-
-    def get_message(self):
-        return self._desc
+class NoSuchMetric(WatcherException):
+    msg_fmt = _('No such metric')
 
 
-class NoSuchMetric(BaseException):
-    def __init__(self, desc):
-        desc = desc or _("No such metric")
-        super(NoSuchMetric, self).__init__(desc)
-
-    def get_message(self):
-        return self._desc
-
-
-class NoDataFound(BaseException):
-    def __init__(self, desc):
-        desc = desc or _("No rows were returned")
-        super(NoDataFound, self).__init__(desc)
-
-    def get_message(self):
-        return self._desc
+class NoDataFound(WatcherException):
+    msg_fmt = _('No rows were returned')
 
 
 class KeystoneFailure(WatcherException):
diff --git a/watcher/decision_engine/model/model_root.py b/watcher/decision_engine/model/model_root.py
index 7ae764328..eb5cda841 100644
--- a/watcher/decision_engine/model/model_root.py
+++ b/watcher/decision_engine/model/model_root.py
@@ -34,12 +34,12 @@ class ModelRoot(object):
     def assert_hypervisor(self, obj):
         if not isinstance(obj, hypervisor.Hypervisor):
             raise exception.IllegalArgumentException(
-                _("'obj' argument type is not valid"))
+                message=_("'obj' argument type is not valid"))
 
     def assert_vm(self, obj):
         if not isinstance(obj, vm.VM):
             raise exception.IllegalArgumentException(
-                _("'obj' argument type is not valid"))
+                message=_("'obj' argument type is not valid"))
 
     def add_hypervisor(self, hypervisor):
         self.assert_hypervisor(hypervisor)