Exception namespace fixes

lib/ApiOperations/Request.php

@@ -21,7 +21,7 @@ protected static function _validateParams($params = null)
                . "method calls.  (HINT: an example call to create a charge "
                . "would be: \"Stripe\\Charge::create(['amount' => 100, "
                . "'currency' => 'usd', 'source' => 'tok_1234'])\")";
-            throw new Error\Api($message);
+            throw new \Stripe\Error\Api($message);
         }
     }
 

lib/StripeObject.php

@@ -415,7 +415,7 @@ public static function emptyValues($obj)
         } elseif ($obj instanceof StripeObject) {
             $values = $obj->_values;
         } else {
-            throw new InvalidArgumentException(
+            throw new \InvalidArgumentException(
                 "empty_values got got unexpected object type: " . get_class($obj)
             );
         }

lib/Util/DefaultLogger.php

@@ -11,7 +11,7 @@ class DefaultLogger implements LoggerInterface
     public function error($message, array $context = [])
     {
         if (count($context) > 0) {
-            throw new Exception('DefaultLogger does not currently implement context. Please implement if you need it.');
+            throw new \Exception('DefaultLogger does not currently implement context. Please implement if you need it.');
         }
         error_log($message);
     }