Added RequestException. It is thrown when request fails.

src/RateRequest/Get.php

@@ -16,7 +16,9 @@ class Get extends Adapter
 		curl_setopt($ch, CURLOPT_TIMEOUT, $this->curl_dl_timeout);
 		$response = curl_exec($ch);
 		curl_close($ch);
-
+		if ($response === false) {
+			throw new RequestException(curl_error($ch));
+		}
 		return $response;
 	}
 }

src/RateRequest/Post.php

@@ -16,6 +16,9 @@ class Post extends Adapter
 		curl_setopt($ch, CURLOPT_CONNECTTIMEOUT_MS, $this->curl_connect_timeout_ms);
 		curl_setopt($ch, CURLOPT_TIMEOUT, $this->curl_dl_timeout);
 		$response = curl_exec($ch);
+		if ($response === false) {
+			throw new RequestException(curl_error($ch));
+		}
 		curl_close($ch);
 
 		return $response;

src/RateRequest/RequestException.php

@@ -0,0 +1,6 @@
+<?php
+
+namespace pdt256\Shipping\RateRequest;
+
+
+class RequestException extends \Exception {}