Tools: Update PyYAML version.

Fixes #2278.

tools/generation/requirements.txt

@@ -1 +1 @@
-PyYAML==3.11
+PyYAML==5.1.2

tools/lint/lib/checks/harnessfeatures.py

@@ -9,7 +9,7 @@ class CheckHarnessFeatures(Check):
 
     def __init__(self):
         with open('./harness/features.yml', 'r') as f:
-            self.include_has_features = yaml.load(f.read())
+            self.include_has_features = yaml.safe_load(f.read())
 
     def comparison_result_lists(self, meta):
 

tools/lint/lib/frontmatter.py

@@ -11,6 +11,6 @@ def parse(src):
         return None
 
     try:
-        return yaml.load(match.group(1))
+        return yaml.safe_load(match.group(1))
     except (yaml.scanner.ScannerError, yaml.parser.ParserError):
         return None

tools/lint/requirements.txt

@@ -1,2 +1,2 @@
-PyYAML==3.11
+PyYAML==5.1.2
 inflect==0.2.5