fix: handle error on service not enabled (#1117)

Fixes #1116 🦕

Don't throw invalid JSON messages for valid JSON.

diff --git a/googleapiclient/http.py b/googleapiclient/http.py
index 0046774..b8e1b8e 100644
--- a/googleapiclient/http.py
+++ b/googleapiclient/http.py
@@ -116,7 +116,9 @@
         try:
             data = json.loads(content.decode("utf-8"))
             if isinstance(data, dict):
-                reason = data["error"]["errors"][0]["reason"]
+                reason = data["error"].get("status")
+                if reason is None:
+                    reason = data["error"]["errors"][0]["reason"]
             else:
                 reason = data[0]["error"]["errors"]["reason"]
         except (UnicodeDecodeError, ValueError, KeyError):