Error in installing app

Hi,

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]: yunohost.app.install
2018-12-13 10:36:19,540 ERROR yunohost.app _fetch_app_from_git - [3752.21] unable to download https://github.com/YunoHost-Apps/my_webapp_ynh/archive/6c3615e5b5224cc1bc12196cf0b440df9fd4ff85.zip
Traceback (most recent call last):
File “/usr/lib/moulinette/yunohost/app.py”, line 1943, in _fetch_app_from_git
‘wget’, ‘-qO’, app_tmp_archive, tarball_url])
File “/usr/lib/python2.7/subprocess.py”, line 186, in check_call
raise CalledProcessError(retcode, cmd)
CalledProcessError: Command '[‘wget’, ‘-qO’, ‘/var/cache/yunohost/from_file.zip’, 'https://github.com/YunoHost-Apps/my_webapp_ynh/archive/6c3615e5b5224cc1bc12196cf0b440df9fd4ff85.zip’]’ returned non-zero exit status 4
2018-12-13 10:36:19,549 INFO geventwebsocket.handler log_request - 127.0.0.1 - - [2018-12-13 10:36:19] “POST /apps HTTP/1.1” 500 164 0.354049

Thanks and Regards,
Kumar.