Ubuntu: Cannot set LC ALL to default locale

Problem

$ sudo dpkg-reconfigure tzdata
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
LANGUAGE = (unset),
LC_ALL = (unset),
LC_PAPER = "zh_TW.UTF-8",
LC_ADDRESS = "zh_TW.UTF-8",
LC_MONETARY = "zh_TW.UTF-8",
LC_NUMERIC = "zh_TW.UTF-8",
LC_TELEPHONE = "zh_TW.UTF-8",
LC_IDENTIFICATION = "zh_TW.UTF-8",
LC_MEASUREMENT = "zh_TW.UTF-8",
LC_TIME = "zh_TW.UTF-8",
LC_NAME = "zh_TW.UTF-8",
LANG = "en_US.UTF-8"
are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
locale: Cannot set LC_ALL to default locale: No such file or directory
/usr/bin/locale: Cannot set LC_ALL to default locale: No such file or directory

---

Fix

$ sudo locale-gen zh\_TW.UTF-8
Generating locales...
zh_TW.UTF-8... done
Generation complete.

$ sudo dpkg-reconfigure locales
Generating locales...
en_US.UTF-8... done
zh_TW.UTF-8... up-to-date
Generation complete.