Account for changes to Cargo.lock format.

servo · bors-servo · Nov 2, 2017 · Oct 31, 2017 · Oct 31, 2017 · Oct 31, 2017
commit b8e44e14b2e5062180f352c0b31d5936329bfb95
diff --git a/python/tidy/servo_tidy/tidy.py b/python/tidy/servo_tidy/tidy.py
@@ -316,7 +316,7 @@ def stdout_redirect(where):
 
 def check_lock(file_name, contents):
     def find_reverse_dependencies(name, content):
-        for package in itertools.chain([content["root"]], content["package"]):
+        for package in itertools.chain([content.get("root", [])], content["package"]):
             for dependency in package.get("dependencies", []):
                 if dependency.startswith("{} ".format(name)):
                     yield package["name"], dependency