When loggin in to my Raspberry Pi, just reinstalled with Raspbian, I noticed these errors when connecting via SSH:

locale: Cannot set LC_CTYPE to default locale: No such file or directory
locale: Cannot set LC_ALL to default locale: No such file or directory

The fix is quite easy. Just regenerate the locales with the command below.

localedef -v -c -i en_US -f UTF-8 en_US.UTF-8