epm-update: update local packages list only if /etc/bash_completion.d is exists

bin/epm-update

@@ -47,6 +47,9 @@ __save_available_packages()
 {
     [ -d "$epm_vardir" ] || return 0
 
+    # update list only if the system supports bash completion
+    [ -d /etc/bash_completion.d ] || return 0
+
     info "Retrieving list of all available packages (for autocompletion) ..."
     load_helper epm-list_available
     short=--short epm_list_available | sort | sudorun tee $epm_vardir/available-packages >/dev/null