Additional logging during failure

[di]

In the process of trying to use the test client, I made a mistake between function types and it caused a failure:

| 2020/10/21 22:30:29 Validating for http...
| 2020/10/21 22:30:29 Framework server started.
| 2020/10/21 22:30:30 HTTP validation started...
| 2020/10/21 22:30:30 Framework server shut down. Wrote logs to serverlog_stdout.txt and serverlog_stderr.txt.
| 2020/10/21 22:30:30 Validation failure: failed to unmarshal json: json: cannot unmarshal object into Go value of type string

It would have been helpful to have more details about what caused the JSON to fail to be unmarshalled here. Perhaps a --verbose flag would include this?

[di]

Similarly when the test function fails for some reason:

| 2020/10/21 23:45:23 Validating for cloudevent...
| 2020/10/21 23:45:23 Framework server started.
| 2020/10/21 23:45:24 CloudEvent validation with CloudEvent requests...
| 2020/10/21 23:45:24 Framework server shut down. Wrote logs to serverlog_stdout.txt and serverlog_stderr.txt.
| 2020/10/21 23:45:24 Validation failure: failed to get response from function for "firebase-auth": failed to send CloudEvent: 500:

Would be helpful to see the 500 response the test client got here.

[kevmoo]

Yes here!