cat command display a warning if no file is selected by pattern

installsystems/image.py

@@ -617,7 +617,10 @@ class PackageImage(Image):
         '''
         Display filename in the tarball
         '''
-        for filename in self._tarball.getnames(glob_pattern=filename):
+        filelist = self._tarball.getnames(glob_pattern=filename)
+        if len(filelist) == 0:
+            warn("No file matching %s" % filename)
+        for filename in filelist:
             arrow(filename)
             out(self._tarball.get_str(filename))