Generate new Locales

perl: warning: Please check that your locale settings:
	LANGUAGE = (unset),
	LC_ALL = (unset),
	LC_PAPER = "de_DE.UTF-8",
	LC_ADDRESS = "de_DE.UTF-8",
	LC_MONETARY = "de_DE.UTF-8",
	LC_NUMERIC = "de_DE.UTF-8",
	LC_TELEPHONE = "de_DE.UTF-8",
	LC_IDENTIFICATION = "de_DE.UTF-8",
	LC_MEASUREMENT = "de_DE.UTF-8",
	LC_CTYPE = "UTF-8",
	LC_TIME = "de_DE.UTF-8",
	LC_NAME = "de_DE.UTF-8",
	LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").

Fix

locale-gen en_US.UTF-8
sudo localedef -i en_US -f UTF-8 en_US.UTF-8
export LANGUAGE=en_US.UTF-8
export LANG=en_US.UTF-8
export LC_ALL=en_US.UTF-8
locale-gen en_US.UTF-8
sudo dpkg-reconfigure locales

References

1. https://www.thomas-krenn.com/de/wiki/Perl_warning_Setting_locale_failed_unter_Debian