(env) $ translate-cli -t zh "This is a pen."
Translation: '' IS AN INVALID SOURCE LANGUAGE . EXAMPLE: LANGPAIR=EN|IT USING 2 LETTER ISO OR RFC3066 LIKE ZH-CN. ALMOST ALL LANGUAGES SUPPORTED BUT SOME MAY HAVE NO CONTENT
translate-cli -f es -t zh "This is a pen." works though.
After installing from source:
translate-cli -f es -t zh "This is a pen."
works though.