Fix deprecation warning about Hashable in py3.7

mongoengine/base/document.py

@@ -1,6 +1,5 @@
 import copy
 import numbers
-from collections import Hashable
 from functools import partial
 
 from bson import ObjectId, json_util
@@ -19,6 +18,7 @@ from mongoengine.base.fields import ComplexBaseField
 from mongoengine.common import _import_class
 from mongoengine.errors import (FieldDoesNotExist, InvalidDocumentError,
                                 LookUpError, OperationError, ValidationError)
+from mongoengine.python_support import Hashable
 
 __all__ = ('BaseDocument', 'NON_FIELD_ERRORS')
 

mongoengine/python_support.py

@@ -19,3 +19,10 @@ if not six.PY3:
         pass
     else:
         StringIO = cStringIO.StringIO
+
+
+if six.PY3:
+    from collections.abc import Hashable
+else:
+    # raises DeprecationWarnings in Python >=3.7
+    from collections import Hashable