Run dialog: Make error message translatable

Allow the error message to be translated.

https://bugzilla.gnome.org/show_bug.cgi?id=597422

js/ui/runDialog.js

@@ -170,7 +170,7 @@ RunDialog.prototype = {
                  * We are only interested in the actual error, so parse that out.
                  */
                 let m = /.+\((.+)\)/.exec(e);
-                let errorStr = "Execution of '" + command + "' failed:\n" + m[1];
+                let errorStr = _("Execution of '%s' failed:").format(command) + "\n" + m[1];
                 this._errorMessage.set_text(errorStr);
                 this._errorBox.show();
             }