warning: setlocale: LC_CTYPE: cannot change locale (UTF-8): No such file or directory fixed

$ cat /etc/environment

LANG=en_US.utf-8 

LC_ALL=en_US.utf-8

For CentOS:

sudo vi /etc/environment

add the following  lines:

LANG=en_US.utf-8
LC_ALL=en_US.utf-8

Or, 

export LC_CTYPE=en_US.UTF-8 

export LC_ALL=en_US.UTF-8

or 

vi  .bash_profile

then add the following lines:

export LC_CTYPE=en_US.UTF-8 

export LC_ALL=en_US.UTF-8