webdriver: error: rename WebDriverError.status_code to error_code

The WebDriver standard uses the term "JSON error code" and "error code" to
refer to the string identifier of the error type.  We should follow suit.

Source-Repo: https://github.com/mozilla/webdriver-rust
Source-Revision: fd03b53eb29dd4dea37f41648196c7888905693f

--HG--
extra : subtree_source : http%3A//tristan.corp.lon2.mozilla.com%3A8000
extra : subtree_revision : 0873788dc46ddbd3cd54c47961cb2116c0379506

testing/webdriver/src/error.rs

@@ -140,8 +140,8 @@ impl WebDriverError {
         }
     }
 
-    pub fn status_code(&self) -> &'static str {
-        self.error.status_code()
+    pub fn error_code(&self) -> &'static str {
+        self.error.error_code()
     }
 
     pub fn http_status(&self) -> StatusCode {
@@ -156,7 +156,7 @@ impl WebDriverError {
 impl ToJson for WebDriverError {
     fn to_json(&self) -> Json {
         let mut data = BTreeMap::new();
-        data.insert("error".into(), self.status_code().to_json());
+        data.insert("error".into(), self.error_code().to_json());
         data.insert("message".into(), self.message.to_json());
         data.insert("stacktrace".into(),
                     format!("{:?}", self.backtrace).to_json());
@@ -168,7 +168,7 @@ impl ToJson for WebDriverError {
 
 impl Error for WebDriverError {
     fn description(&self) -> &str {
-        self.status_code()
+        self.error_code()
     }
 
     fn cause(&self) -> Option<&Error> {