Document the ValidationError class

docs/apireference.rst

@@ -31,6 +31,9 @@ Documents
 .. autoclass:: mongoengine.document.MapReduceDocument
   :members:
 
+.. autoclass:: mongoengine.ValidationError
+  :members:
+
 Querying
 ========
 

docs/guide/defining-documents.rst

@@ -98,7 +98,7 @@ arguments can be set on all fields:
 
 :attr:`required` (Default: False)
     If set to True and the field is not set on the document instance, a
-    :class:`~mongoengine.base.ValidationError` will be raised when the document is
+    :class:`~mongoengine.ValidationError` will be raised when the document is
     validated.
 
 :attr:`default` (Default: None)

docs/guide/document-instances.rst

@@ -91,5 +91,5 @@ is an alias to :attr:`id`::
 .. note::
 
    If you define your own primary key field, the field implicitly becomes
-   required, so a :class:`ValidationError` will be thrown if you don't provide
-   it.
+   required, so a :class:`~mongoengine.ValidationError` will be thrown if
+   you don't provide it.