Misc fixes and improve coverage

src/protean/__init__.py

@@ -2,6 +2,7 @@
 
 from .core.aggregate import apply, atomic_change
 from .core.entity import invariant
+from .core.event import BaseEvent
 from .core.model import BaseModel
 from .core.queryset import Q, QuerySet
 from .core.unit_of_work import UnitOfWork
@@ -12,6 +13,7 @@
 from .utils.mixins import handle
 
 __all__ = [
+    "BaseEvent",
     "BaseModel",
     "Domain",
     "Engine",

src/protean/exceptions.py

@@ -79,23 +79,6 @@ class ValidationError(ProteanException):
     """
 
 
-class UsecaseExecutionError(Exception):
-    """Raised when a failure response is encountered on executing a usecase
-
-    :param value: a tuple comprising of the error code and error message
-    :type value: tuple
-    :param orig_exc: Optional original exception raised in the usecase
-    :param orig_trace: Optional trace of the original exception in the usecase
-    """
-
-    def __init__(self, value, orig_exc=None, orig_trace=None, **kwargs):
-        self.value = value
-        self.orig_exc = orig_exc
-        self.orig_trace = orig_trace
-
-        super().__init__(**kwargs)
-
-
 class SendError(Exception):
     """Raised on email dispatch failure."""
 

tests/reflection/test_fields.py

@@ -3,25 +3,25 @@
 from protean.core.aggregate import BaseAggregate
 from protean.exceptions import IncorrectUsageError
 from protean.fields import Integer, String
-from protean.utils.reflection import declared_fields
+from protean.utils.reflection import fields
 
 
 class Person(BaseAggregate):
     name = String(max_length=50, required=True)
     age = Integer()
 
 
-def test_declared_fields():
-    assert len(declared_fields(Person)) == 3
-    assert all(key in declared_fields(Person) for key in ["name", "age", "id"])
+def test_fields():
+    assert len(fields(Person)) == 4
+    assert all(key in fields(Person) for key in ["_version", "name", "age", "id"])
 
 
 def test_fields_on_non_element():
     class Dummy:
         pass
 
     with pytest.raises(IncorrectUsageError) as exception:
-        declared_fields(Dummy)
+        fields(Dummy)
 
     assert exception.value.messages == {
         "field": [