Fixing various docstrings
diff --git a/google/auth/exceptions.py b/google/auth/exceptions.py
index dedde9e..2be9fd6 100644
--- a/google/auth/exceptions.py
+++ b/google/auth/exceptions.py
@@ -19,7 +19,7 @@
     """Base class for all google.auth errors."""
 
 
-class TransportError(Exception):
+class TransportError(GoogleAuthError):
     """Used to indicate an error occurred during an HTTP request."""