Steps to reproduce

You need a valid API key, then you can send a simply CURL request for testing:
curl "https://translation.googleapis.com/language/translate/v2?key=<enter key here>&q=survey&source=en&target=<enter language code>"

Expected result

API call should return the translation of "survey" in the target language defined.

Actual result

API returns this for an invalid/valid target language code:

Wrong code "hat":
curl "https://translation.googleapis.com/language/translate/v2?key=<enter key here>&q=survey&source=en&target=hat"
{
"error": {
"code": 400,
"message": "Invalid Value",
"errors": [
{
"message": "Invalid Value",
"domain": "global",
"reason": "invalid"
}
],
"details": [
{
"@type": "type.googleapis.com/google.rpc.BadRequest",
"fieldViolations": [
{
"field": "target",
"description": "Target language: hat"
}
]
}
]
}
}

Correct code "ht":
curl "https://translation.googleapis.com/language/translate/v2?key=<enter key here>&q=survey&source=en&target=ht"
{
"data": {
"translations": [
{
"translatedText": "sondaj"
}
]
}
}