Thank you for your help guys.

It works now but I don't know what tip has done something. I've deleted repos and I've edited mce.ini but this one had already the line dbus-signal-powerkey_double_ind for PowerKeyDoubleAction.
But there was a line just below with "PowerKeyDoubleAction=" so I've written again after the "=" dbus-signal-powerkey_double_ind.

Then I've tried to uninstall and reinstall the app, rebooted the phone and finally it works. Thank you again !