Connection error with heroku db:push with postgresql

I have suddenly started seeing this strange error when trying to push my database to heroku.

> heroku db:push
Auto-detected local database: postgres://infinity:infinity@localhost/infinity_development?encoding=utf8
Failed to connect to database:
Sequel::DatabaseConnectionError -> TypeError wrong argument type String (expected Array)

My app works fine - the credenti开发者_如何学编程als are all set locally.

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Hmmm ... once again this all just started magically working.