fix_inspect_deprecated_warning: inspect.getargspec is deprecated since Python 3.0.

rest_framework/fields.py

@@ -56,10 +56,18 @@ def is_simple_callable(obj):
     if not (function or method):
         return False
 
+    if six.PY2:
         args, _, _, defaults = inspect.getargspec(obj)
         len_args = len(args) if function else len(args) - 1
         len_defaults = len(defaults) if defaults else 0
         return len_args <= len_defaults
+    else:
+        sig = inspect.signature(obj)
+        for name, param in sig.parameters.items():
+            if param.default is not inspect.Parameter.empty:
+                return False
+
+        return True
 
 
 def get_attribute(instance, attrs):