fix: name error

Author: BobTheBuidler

mypy/checkpattern.py

@@ -796,7 +796,7 @@ def get_var(expr: Expression) -> Var:
     Warning: this in only true for expressions captured by a match statement.
     Don't call it from anywhere else
     """
-    assert isinstance(expr, NameExpr), node
+    assert isinstance(expr, NameExpr), expr
     node = expr.node
     assert isinstance(node, Var), node
     return node