Update default file pattern for grader-convert

[meffmadd]

Is your feature request related to a problem? Please describe. Right now we only convert notebooks in the current directory by using *.ipynb as the glob pattern.

Describe the solution you'd like The default pattern should be changed to **/*.ipynb so that notebooks in subdirectories are also converted. This is also necessary for grader-labextension if it does explicitly overwrite the default.

[joseftaha]

Idea: glob.glob returns the list of notebooks to convert based on the given pattern. This function accepts a booelan flag "recursive" which when set to true, let the pattern ** match any files and zero or more directories and sub-directories. Setting the default pattern to **/*.ipynb and including a recursive=True should convert all notebooks in current dir and subdirs.

• Change default pattern to */.ipynb in baseapp.py

  file_pattern = Unicode("**/*.ipynb", allow_none=False).tag(config=True)

• Setting the recursive flag True in init_notebooks in base.py

  def init_notebooks(self) -> None:
      self.notebooks = []
      notebook_glob = self._format_source()
      self.notebooks = glob.glob(notebook_glob, recursive=True) # Change
      if len(self.notebooks) == 0:
          self.log.warning("No notebooks were matched by '%s'", notebook_glob)