From 431b0c3fe0315e5b870cd26cccb680b8b9d9731e Mon Sep 17 00:00:00 2001
From: kimamula <kenji.imamula@gmail.com>
Date: Sat, 8 Feb 2020 11:41:48 +0900
Subject: [PATCH] fix: set Content-Type header in the request to signBlob API
 to avoid Invalid JSON payload error

---
 google/auth/iam.py | 2 +-
 tests/test_iam.py  | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/google/auth/iam.py b/google/auth/iam.py
index 0ab5b5549..4077adb92 100644
--- a/google/auth/iam.py
+++ b/google/auth/iam.py
@@ -69,7 +69,7 @@ def _make_signing_request(self, message):
 
         method = "POST"
         url = _SIGN_BLOB_URI.format(self._service_account_email)
-        headers = {}
+        headers = {"Content-Type": "application/json"}
         body = json.dumps(
             {"bytesToSign": base64.b64encode(message).decode("utf-8")}
         ).encode("utf-8")
diff --git a/tests/test_iam.py b/tests/test_iam.py
index 52ab9bd82..eeba3de22 100644
--- a/tests/test_iam.py
+++ b/tests/test_iam.py
@@ -86,6 +86,8 @@ def test_sign_bytes(self):
         returned_signature = signer.sign("123")
 
         assert returned_signature == signature
+        kwargs = request.call_args.kwargs
+        assert kwargs.get("headers").get("Content-Type") == "application/json"
 
     def test_sign_bytes_failure(self):
         request = make_request(http_client.UNAUTHORIZED)