Error: could not find a distribution template for elementary/juno

Question

I have a problem on my elementary os Juno. So when I want to add a ppa, it answers me :

arthur@arthur:~$ sudo add-apt-repository ppa:mpstark/elementary-tweaks-daily
Traceback (most recent call last):
  File "/usr/bin/add-apt-repository", line 107, in <module>
    sp = SoftwareProperties(options=options)
  File "/usr/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 117, in __init__
    self.reload_sourceslist()
  File "/usr/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 612, in reload_sourceslist
    self.distro.get_sources(self.sourceslist)    
  File "/usr/lib/python3/dist-packages/aptsources/distro.py", line 93, in get_sources
    (self.id, self.codename))
aptsources.distro.NoDistroTemplateException: Error: could not find a distribution template for elementary/juno

And it's the exactly same error when I tried t launch the "Software and Updates" app...

arthur@arthur:~$ software-properties-gtk
Traceback (most recent call last):
  File "/usr/bin/software-properties-gtk", line 100, in <module>
    app = SoftwarePropertiesGtk(datadir=options.data_dir, options=options, file=file)
  File "/usr/lib/python3/dist-packages/softwareproperties/gtk/SoftwarePropertiesGtk.py", line 115, in __init__
    SoftwareProperties.__init__(self, options=options, datadir=datadir)
  File "/usr/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 117, in __init__
    self.reload_sourceslist()
  File "/usr/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 612, in reload_sourceslist
    self.distro.get_sources(self.sourceslist)    
  File "/usr/lib/python3/dist-packages/aptsources/distro.py", line 93, in get_sources
    (self.id, self.codename))
aptsources.distro.NoDistroTemplateException: Error: could not find a distribution template for elementary/juno

So , what should I do ? Thanks, Arthur