old_contents: class HQAccountingSetupError(Exception):
      pass
  
  
  class LineItemError(Exception):
      pass
  
  
  class InvoiceError(Exception):
      pass
  
  
  class CreditLineError(Exception):
      pass
  
new_contents: class AccountingError(Exception):
      pass
  
  
  class LineItemError(Exception):
      pass
  
  
  class InvoiceError(Exception):
      pass
  
  
  class CreditLineError(Exception):
      pass
  
subject: simplify exception name to AccountingError