Error in installing app


All of a sudden today, when i tried to install an app, it says 'unable to download…" and application is not getting installed from yunohost admin. I even tried from the terminal prompt with the command and still same error.

Below is the error i am getting:
2018-12-13 10:36:19,356 INFO moulinette.actionsmap process - processing action [3752.21]:
2018-12-13 10:36:19,540 ERROR _fetch_app_from_git - [3752.21] unable to download
Traceback (most recent call last):
File “/usr/lib/moulinette/yunohost/”, line 1943, in _fetch_app_from_git
‘wget’, ‘-qO’, app_tmp_archive, tarball_url])
File “/usr/lib/python2.7/”, line 186, in check_call
raise CalledProcessError(retcode, cmd)
CalledProcessError: Command '[‘wget’, ‘-qO’, ‘/var/cache/yunohost/’, '’]’ returned non-zero exit status 4
2018-12-13 10:36:19,549 INFO geventwebsocket.handler log_request - - - [2018-12-13 10:36:19] “POST /apps HTTP/1.1” 500 164 0.354049

Thanks and Regards,