fix f-string prefix

Co-authored-by: Piotr Sawicki <[email protected]>

Author: BobTheBuidler

mypyc/ir/ops.py

@@ -1047,7 +1047,7 @@ def __init__(self, src: Value, index: int, line: int = -1, *, borrow: bool = Fal
         super().__init__(line)
         assert isinstance(
             src.type, RTuple
-        ), "TupleGet only operates on tuples, not {type(src.type).__name__}"
+        ), f"TupleGet only operates on tuples, not {type(src.type).__name__}"
         src_len = len(src.type.types)
         self.src = src
         self.index = index