Avoid mutating a line that will cause an infinite loop if mutated
@@ -423,7 +423,7 @@ def __to_rpn(tokens):
stack.pop()
result_q.append(t2)
else: # pragma: no cover
- break
+ break # pragma: no mutate
stack.append((token, PRECEDENCE[token]))
while stack:
result_q.append(stack.pop()[0])
