Usage of But in "Never a trouble but brought profit to somebody."

Question

I read the following in a book (A Crown of Swords by Robert Jordan):

Refugees filled the city, and merchants and traders of every sort. Never a trouble but brought profit to somebody.

What does that mean? I think it's one of two things, but I can't work out which (not a native speaker):

• The refugees and traders are never a problem but somebody will profit from them.

• There is never a sort of trouble that people will not make a profit out of.

The subtlety is lost on me, so can a more skilled English speaker (or writer) help me out?

Answer 1

But is used as a "quasi-relative pronoun/negative relative pronoun" that has a negative connotation in itself. It has the following meaning in Wiktionary:

Except that (introducing a subordinate clause which qualifies a negative statement); also, with omission of the subject of the subordinate clause, acting as a negative relative, "except one that", "except such that".

Therefore,

(There was) Never a trouble but brought profit to somebody.

can be rephrased to:

(There was) Never a trouble that didn't bring profit to somebody.
Every trouble brought profit to somebody.

You probably heard of this expression.

There is no rule but has some exceptions.

There is no rule that doesn't have some exceptions. Every rule has some exceptions.

Answer 2

Not your first version. Your second version is close.

The idea is that the city is so filled with both (needy) refugees and merchants and traders of every sort that all troubles are an opportunity for profit for someone. This would not be the case were there fewer refugees or fewer merchants (economical 'critical masses' need to be reached, perhaps).