[gem.appimage] improvement: hiding the app's launching output

CHANGELOG.md

@@ -10,6 +10,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
     - manual installation
       - adding generic file filter extension (.*) since some desktop environments filters are case sensitive (https://github.com/vinifmor/bauh/issues/185)[#185]
       - generating a default **.desktop** file based on the installation form for AppImage files that provide empty desktop entries (https://github.com/vinifmor/bauh/issues/186)[#186]
+    - hiding the app's launching output
   
 ### Fixes
 - AppImage

bauh/gems/appimage/controller.py

@@ -715,7 +715,8 @@ class AppImageManager(SoftwareManager):
             appimag_path = util.find_appimage_file(installation_dir)
 
             if appimag_path:
-                subprocess.Popen(args=[appimag_path], shell=True, env={**os.environ})
+                subprocess.Popen(args=[appimag_path], shell=True, env={**os.environ},
+                                 stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL, stdin=subprocess.DEVNULL)
             else:
                 self.logger.error("Could not find the AppImage file of '{}' in '{}'".format(pkg.name, installation_dir))