message: add dummy file param to fix jupyter
  testshell in jupyter was failing due to an extra arg.
  this adds a dummy -f param, which allows TestShell to
  be used in a command line or jupyter environment
diff: @@ -194,6 +194,10 @@ class BitcoinTestFramework(metaclass=BitcoinTestMetaClass):
  help="Run test using legacy wallets", dest='descriptors')
  self.add_options(parser)
  + # Running TestShell in a Jupyter notebook causes an additional -f argument
  + # To keep TestShell from failing with an "unrecognized argument" error, we add a dummy "-f" argument
  + # source: https://stackoverflow.com/questions/48796169/how-to-fix-ipykernel-launcher-py-error-unrecognized-arguments-in-jupyter/56349168#56349168
  + parser.add_argument("-f", "--fff", help="a dummy argument to fool ipython", default="1")
  self.options = parser.parse_args()
  self.options.previous_releases_path = previous_releases_path
  