old_contents: class ParserError(Exception):
      pass
  
  
  class AuthError(Exception):
      pass
  
new_contents: class BasePyVKAError(Exception):
      pass
  
  
  class ParserError(BasePyVKAError):
      pass
  
  
  class AuthError(BasePyVKAError):
      pass
  
subject: improve exceptions: add base package exception