Added integration to Ubuntu AppIndicator

[ronymesquita]

The idea is to create a shortcut and integration with GNOME Shell and Ubuntu AppIndicator.
The image shows a screenshot on Ubuntu 20.04 with the code.

Executing from terminal, the error below is show when clicked to open preferences dialog.
The clean operation not fail and this code can works when not called from terminal, but I doesn't have tested.

Traceback (most recent call last):
  File "/home/rony/git/bleachbit/bleachbit/GUI.py", line 271, in cb_preferences_dialog
    pref = self.get_preferences_dialog()
  File "/home/rony/git/bleachbit/bleachbit/GUI.py", line 267, in get_preferences_dialog
    return self._window.get_preferences_dialog()
AttributeError: 'NoneType' object has no attribute 'get_preferences_dialog'

[az0]

@ronymesquita
Are you able to please fix the traceback and the merge conflict?

[ronymesquita]

Hello @az0.
I fixed the traceback and merged the conflict.
Please, can you take a look?

[az0]

@ronymesquita

Thank you for making that change quickly.

On my system, the application fails to start, so please allow graceful fallback.

$ python3 bleachbit.py 
Traceback (most recent call last):
  File "/bleachbit/bleachbit/GUI.py", line 48, in <module>
    from gi.repository import AyatanaAppIndicator3 as AppIndicator
  File "/usr/lib/python3/dist-packages/gi/importer.py", line 136, in load_module
    raise ImportError('cannot import name %s, '
ImportError: cannot import name AyatanaAppIndicator3, introspection typelib not found

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/bleachbit/bleachbit/GUI.py", line 51, in <module>
    from gi.repository import AppIndicator3 as AppIndicator
  File "/usr/lib/python3/dist-packages/gi/importer.py", line 136, in load_module
    raise ImportError('cannot import name %s, '
ImportError: cannot import name AppIndicator3, introspection typelib not found

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/bleachbit/bleachbit.py", line 55, in <module>
    import bleachbit.GUI
  File "/bleachbit/bleachbit/GUI.py", line 53, in <module>
    from gi.repository import AppIndicator
  File "/usr/lib/python3/dist-packages/gi/importer.py", line 136, in load_module
    raise ImportError('cannot import name %s, '
ImportError: cannot import name AppIndicator, introspection typelib not found

[ronymesquita]

@az0

This time, the import has been changed to work when the appindicator is unavailable.