Emit FutureWarning whenever necessary

Author: alexitkes

pandas/util/_decorators.py

@@ -238,6 +238,22 @@ def deprecate_nonkeyword_arguments(
     def decorate(func):
         @wraps(func)
         def wrapper(*args, **kwargs):
+            if isinstance(allowed_args, int) and len(args) > allowed_args:
+                msg = (
+                    "After version %s all arguments of %s "
+                    "except for the first %i will be keyword-only"
+                ) % (version, func.__name__, allowed_args)
+            elif isinstance(allowed_args, (list, tuple)) and len(args) > len(
+                allowed_args
+            ):
+                msg = (
+                    "After version %s all arguments of %s "
+                    "except for (%s) will be keyword-only"
+                ) % (version, func.__name__, ", ".join(allowed_args))
+            else:
+                msg = None
+            if msg:
+                warnings.warn(msg, FutureWarning, stacklevel=stacklevel)
             return func(*args, **kwargs)
 
         return wrapper