render unions with new union syntax in output messages

Author: KotlinIsland

CHANGELOG.md

@@ -1,6 +1,8 @@
 # Basedmypy Changelog
 
 ## [Unreleased]
+### Added
+- Unions in output messages show with new syntax
 
 ## [1.0.0]
 ### Added

mypy/types.py

@@ -1873,6 +1873,9 @@ def __init__(self, items: Sequence[Type], line: int = -1, column: int = -1,
     def __hash__(self) -> int:
         return hash(frozenset(self.items))
 
+    def __repr__(self):
+        return " | ".join(map(repr, self.items))
+
     def __eq__(self, other: object) -> bool:
         if not isinstance(other, UnionType):
             return NotImplemented