Use marshmallow 3's from_dict if available

src/webargs/dict2schema.py

@@ -1,20 +1,17 @@
 # -*- coding: utf-8 -*-
 import marshmallow as ma
 
-from webargs.compat import MARSHMALLOW_VERSION_INFO
-
 
 def dict2schema(dct, schema_class=ma.Schema):
     """Generate a `marshmallow.Schema` class given a dictionary of
     `Fields <marshmallow.fields.Field>`.
     """
+    if hasattr(schema_class, "from_dict"):  # marshmallow 3
+        return schema_class.from_dict(dct)
     attrs = dct.copy()
 
     class Meta(object):
-        if MARSHMALLOW_VERSION_INFO[0] < 3:
-            strict = True
-        else:
-            register = False
+        strict = True
 
     attrs["Meta"] = Meta
     return type(str(""), (schema_class,), attrs)