Bug 1417821 - Add element click intercepted error to WPT WebDriver client. r=whimboo

MozReview-Commit-ID: 1BFa4L7QW9d

--HG--
extra : rebase_source : 5f97db90c176a452e910ac23ef00f534e23819ed

testing/web-platform/tests/tools/webdriver/webdriver/error.py

@@ -21,6 +21,11 @@ class WebDriverException(Exception):
             "%s" % (self.status_code, self.http_status, self.stacktrace))
 
 
+class ElementClickInterceptedException(WebDriverException):
+    http_status = 400
+    status_code = "element click intercepted"
+
+
 class ElementNotSelectableException(WebDriverException):
     http_status = 400
     status_code = "element not selectable"