Permit does not revert for tokens that do not implement it.

Callers should not rely on permit to revert for arbitrary tokens especially if permit is used as a security check. Tokens which do not revert on permit either do not implement it or have a non-reverting fallback function. Most notable among them is WETH. In the case of Pool Together, permit is used to allow the vault to make deposits on behalf of users but this call will always fail because the approval part of the permit is never executed, thereby bricking a main functionality of the protocol