Improve curl error string handling.

Introduce kore_curl_strerror(), use this in kore_curl_logerror()
instead of assuming our errbuf has been populated.

Also use it in the python httpclient when throwing an exception rather
then looking at the errbuf member which may or may not be empty.

include/kore/curl.h

@@ -91,6 +91,8 @@ void	kore_curl_bind_request(struct kore_curl *, struct http_request *);
 void	kore_curl_bind_callback(struct kore_curl *,
 	    void (*cb)(struct kore_curl *, void *), void *);
 
+const char	*kore_curl_strerror(struct kore_curl *);
+
 #if defined(__cplusplus)
 }
 #endif

src/curl.c

@@ -244,11 +244,24 @@ kore_curl_success(struct kore_curl *client)
 	return (client->result == CURLE_OK);
 }
 
+const char *
+kore_curl_strerror(struct kore_curl *client)
+{
+	const char	*err;
+
+	if (client->errbuf[0] != '\0')
+		err = &client->errbuf[0];
+	else
+		err = curl_easy_strerror(client->result);
+
+	return (err);
+}
+
 void
 kore_curl_logerror(struct kore_curl *client)
 {
-	kore_log(LOG_NOTICE, "curl error: %s -> %s",
-	    client->url, client->errbuf);
+	kore_log(LOG_NOTICE, "curl error: %s -> %s", client->url,
+	    kore_curl_strerror(client));
 }
 
 void

src/python.c

@@ -4329,7 +4329,7 @@ pyhttp_client_op_iternext(struct pyhttp_client_op *op)
 
 	if (!kore_curl_success(&op->curl)) {
 		PyErr_Format(PyExc_RuntimeError, "request to '%s' failed: %s",
-		    op->curl.url, op->curl.errbuf);
+		    op->curl.url, kore_curl_strerror(&op->curl));
 		return (NULL);
 	}