PARIS — When French politician Marine Le Pen needed cash for her far-right party, an obscure Russian bank agreed to help. Four years later, the bank has gone bust. The owner is facing a warrant for his arrest. Former Russian military officers are demanding money. And the party’s treasurer is sending off some $165,000 every few months to a woman in Moscow, unsure of where the payments ultimately will go. The money failed to deliver Le Pen the French presidency in last year’s election, denying the Kremlin a powerful ally in the heart of Europe.