remove misleading raise_for_status (GoogleCloudPlatform#2948)

When the response has error, the error detail is not exposed because of raise_for_status, so remove it and show the detailed message.

For instance, the detailed error is UNAUTHENTICATED:Method doesn't allow unregistered callers (callers without established identity). Please use API Key or other form of API consumer identity to call this API.
but we only got requests.exceptions.HTTPError: 401 Client Error: Unauthorized for url.

Author: TAOXUY

endpoints/getting-started/clients/google-jwt-client.py

@@ -68,9 +68,9 @@ def make_jwt_request(signed_jwt, url='https://your-endpoint.com'):
         'content-type': 'application/json'
     }
     response = requests.get(url, headers=headers)
-
+    print(response.status_code, response.content)
     response.raise_for_status()
-    return response.text
+
 # [END endpoints_jwt_request]
 
 
@@ -96,4 +96,4 @@ def make_jwt_request(signed_jwt, url='https://your-endpoint.com'):
                                args.sa_email,
                                args.audience,
                                expiry_length)
-    print(make_jwt_request(keyfile_jwt, args.host))
+    make_jwt_request(keyfile_jwt, args.host)