I tried to install Python using pyenv but came across the following error:

vagrant@vagrant-ubuntu-trusty-64:~$ pyenv install 2.7.8
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
	LANGUAGE = (unset),
	LC_ALL = (unset),
	LC_CTYPE = "UTF-8",
	LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").

For those which are unset, set the environmental variables in .bashrc or .bash_profile.

export LANGUAGE=en_US.UTF-8
export LC_ALL=en_US.UTF-8

Re-login and try again.

Done =)

Reference: perl: warning: Please check that your locale settings ubuntu