https://github.com/vcstools/vcstools/issues/158
https://bugs.gentoo.org/698668

Index: vcstools-0.1.42/src/vcstools/tar.py
===================================================================
--- vcstools-0.1.42.orig/src/vcstools/tar.py
+++ vcstools-0.1.42/src/vcstools/tar.py
@@ -77,7 +77,7 @@ class TarClient(VcsClientBase):
         """
         if self.detect_presence():
             with open(self.metadata_path, 'r') as metadata_file:
-                metadata = yaml.load(metadata_file.read())
+                metadata = yaml.full_load(metadata_file.read())
                 if 'url' in metadata:
                     return metadata['url']
         return None
@@ -165,7 +165,7 @@ class TarClient(VcsClientBase):
 
         if self.detect_presence():
             with open(self.metadata_path, 'r') as metadata_file:
-                metadata = yaml.load(metadata_file.read())
+                metadata = yaml.full_load(metadata_file.read())
                 if 'version' in metadata:
                     return metadata['version']
         return None