Don't swallow AssertionErrors

Most validation errors are in fact the user's problem, but in the case of
an AssertionError that's a real problem with Heat. We should return 500
status codes and log the tracebacks, not wrap the in validation exceptions.

Change-Id: I71d91a5413d7f026b332014487583b7f2762b322

heat/engine/resources/stack_resource.py

@@ -66,6 +66,8 @@ class StackResource(resource.Resource):
                 self.child_params())
             nested_stack.strict_validate = False
             nested_stack.validate()
+        except AssertionError:
+            raise
         except Exception as ex:
             raise exception.StackValidationFailed(
                 error=_("Failed to validate"),

heat/engine/service.py

@@ -556,6 +556,8 @@ class EngineService(service.Service):
     def _validate_new_stack(self, cnxt, stack_name, parsed_template):
         try:
             parsed_template.validate()
+        except AssertionError:
+            raise
         except Exception as ex:
             raise exception.StackValidationFailed(message=six.text_type(ex))
 

heat/engine/stack.py

@@ -642,8 +642,10 @@ class Stack(collections.Mapping):
             try:
                 result = res.validate()
             except exception.HeatException as ex:
-                LOG.info(ex)
+                LOG.debug('%s', ex)
                 raise ex
+            except AssertionError:
+                raise
             except Exception as ex:
                 LOG.exception(_LE("Exception: %s"), ex)
                 raise exception.StackValidationFailed(
@@ -669,7 +671,9 @@ class Stack(collections.Mapping):
                     path=[self.t.OUTPUTS],
                     message=message)
             except exception.StackValidationFailed as ex:
-                raise ex
+                raise
+            except AssertionError:
+                raise
             except Exception as ex:
                 raise exception.StackValidationFailed(
                     error='Output validation error',
@@ -1555,6 +1559,8 @@ class Stack(collections.Mapping):
     def resolve_static_data(self, snippet):
         try:
             return self.t.parse(self, snippet)
+        except AssertionError:
+            raise
         except Exception as ex:
             raise exception.StackValidationFailed(
                 message=encodeutils.safe_decode(six.text_type(ex)))