Bug 1469999 - Use yaml.safe_load() for loading linter config file; r=ahal

yaml.load() is unsafe and can lead to arbitrary code execution via
syntax like `!!python/object/apply:os.system`. yaml.safe_load() is
more reasonable.

Differential Revision: https://phabricator.services.mozilla.com/D1738

--HG--
extra : rebase_source : 597c07b3c1538dc27ad6f46e01cdb7f48755d0bc
extra : histedit_source : 131d570f8ac1ee047487cba54822dbf20abf6681

python/mozlint/mozlint/parser.py

@@ -90,7 +90,7 @@ class Parser(object):
             raise LinterParseError(path, "Invalid filename, linters must end with '.yml'!")
 
         with open(path) as fh:
-            config = yaml.load(fh)
+            config = yaml.safe_load(fh)
 
         if not config:
             raise LinterParseError(path, "No lint definitions found!")