get_response() could be more verbose with errors

[patrickmj]

The minimal thing to do is to change

drs-toolkit-wp-plugin/drs-tk.php

Lines 832 to 834 in c5a9286

	// if it returns a 403 it will return no $output
	curl_setopt($ch, CURLOPT_FAILONERROR, 1);
	$output = curl_exec($ch);

to turn FAILONERROR off. But that will entail significant changes to the functions that use get_response() so that they can respond to whatever gets passed back to them. Or, some additional work just within that function to log details about the error and pass back a generic error message.

This came up trying to debug an empty response from DPLA in these lines

    $data = get_response($url);
    $json = json_decode($data);
    
    if (isset($json->error)) {
      wp_send_json(json_encode( "There was an error: " . $json->error));
      wp_die();
      return;
    }

Because get_response() returns nothing on a 403, the error handling never kicked in, since json_decode() barfed on the empty $data.