BUG: Improve error handling in Index class for level mismatch

Author: vgnshiyer

pandas/core/indexes/base.py

@@ -2088,9 +2088,14 @@ def _validate_index_level(self, level) -> None:
         verification must be done like in MultiIndex.
 
         """
+        mismatch_error_msg = (
+            f"Requested level ({level}) does not match index name ({self.name})"
+        )
         if lib.is_integer(level):
-            if isinstance(self.name, int) and self.name == level:
+            if lib.is_integer(self.name) and self.name == level:
                 return
+            if lib.is_integer(self.name):
+                raise KeyError(mismatch_error_msg)
             if level < 0 and level != -1:
                 raise IndexError(
                     "Too many levels: Index has only 1 level, "
@@ -2101,9 +2106,6 @@ def _validate_index_level(self, level) -> None:
                     f"Too many levels: Index has only 1 level, not {level + 1}"
                 )
             return
-        mismatch_error_msg = (
-            f"Requested level ({level}) does not match index name ({self.name})"
-        )
         if isna(level) and isna(self.name):
             if not is_matching_na(level, self.name):
                 raise KeyError(mismatch_error_msg)