Warn about circular dependencies

[Pandapip1]

If EIP-X requires EIP-Y, and EIP-Y requires EIP-X, then eipw should give a warning. Same if EIP-X requires EIP-Y requires EIP-Z requires EIP-X, or etc...

[SamWilsn]

This is probably a stupid question, but why?

[Pandapip1]

One can't move the status of any of them beyond the highest level status of all of them.

[Pandapip1]

If EIP-X is Draft and EIP-Y is also Draft, then neither can move higher due to the other not being stable enough.

If EIP-X is Review and EIP-Y is Draft, EIP-Y can be moved to Review but no higher due to EIP-X not being stable enough.

[SamWilsn]

Sounds like we already have a lint then ;)

Jokes aside, yeah, this is an issue (though I think a minor one?)

Unfortunately it will make eipw slower, or a bit more complicated (i.e. build a graph of EIPs.)

[Pandapip1]

It runs in about 2 seconds anyways. Even if it adds another 2 seconds (worst-case) I'd like it.