Prevent remote code execution

yaml.load() allows the provider of the yaml data (in this case: the monitored
host) to run arbitrary commands.

src/main/python/monitoring_config_generator/yaml_tools/readers.py

@@ -57,7 +57,7 @@ def get_from_header(field):
         return response.headers[field] if field in response.headers else None
 
     if response.status_code == 200:
-        yaml_config = yaml.load(response.content)
+        yaml_config = yaml.safe_load(response.content)
         etag = get_from_header('etag')
         mtime = get_from_header('last-modified')
         mtime = datetime.datetime.strptime(mtime, '%a, %d %b %Y %H:%M:%S %Z').strftime('%s') if mtime else int(time())