FIX-#7062: Update exception message for aggregate function (#7063)

Signed-off-by: Anatoly Myachev <anatoly.myachev@intel.com>

modin/pandas/base.py

@@ -414,7 +414,7 @@ def error_raiser(msg, exception=Exception):
             if isinstance(fn, str):
                 if not (hasattr(self, fn) or hasattr(np, fn)):
                     on_invalid(
-                        f"{fn} is not valid function for {type(self)} object.",
+                        f"'{fn}' is not a valid function for '{type(self).__name__}' object",
                         AttributeError,
                     )
             elif not callable(fn):

modin/pandas/test/test_series.py

@@ -734,7 +734,12 @@ def test_aggregate_error_checking(data):
         lambda series: series.aggregate("cumprod"),
     )
     eval_general(
-        modin_series, pandas_series, lambda series: series.aggregate("NOT_EXISTS")
+        modin_series,
+        pandas_series,
+        lambda series: series.aggregate("NOT_EXISTS"),
+        raising_exceptions=AttributeError(
+            "'NOT_EXISTS' is not a valid function for 'Series' object"
+        ),
     )