text: Title: [BUG] ValueError in _RepeatingBasis
  Body: I was running code coverage to see what code was not covered. 
  
  ![image](https://user-images.githubusercontent.com/1019791/78458623-275f4500-76b3-11ea-8d0c-f337768faf6d.png)
  
  @RensDimmendaal it feels like the message in the error is off, would I be correct? If so, this might be a great beginner issue. 