exceptions: Make more errors RepositoryErrors

Try to make errors derive from RepositoryError if they can be the
result of malicious or malfunctioning remote repository: The idea
here is that client can handle just RepositoryError instead of
individual errors (as it cannot do anything about any of them).

Also improve variable naming.

This is backwards compatible.

Signed-off-by: Jussi Kukkonen <[email protected]>

tuf/exceptions.py

@@ -66,7 +66,11 @@ class UnsupportedAlgorithmError(Error):
   """Indicate an error while trying to identify a user-specified algorithm."""
 
 
-class BadHashError(Error):
+class RepositoryError(Error):
+  """Indicate an error with a repository's state, such as a missing file."""
+
+
+class BadHashError(RepositoryError):
   """Indicate an error while checking the value of a hash object."""
 
   def __init__(self, expected_hash, observed_hash):
@@ -89,12 +93,6 @@ def __repr__(self):
     #     repr(self.observed_hash) + ')')
 
 
-
-
-class BadVersionNumberError(Error):
-  """Indicate an error for metadata that contains an invalid version number."""
-
-
 class BadPasswordError(Error):
   """Indicate an error after encountering an invalid password."""
 
@@ -103,8 +101,8 @@ class UnknownKeyError(Error):
   """Indicate an error while verifying key-like objects (e.g., keyids)."""
 
 
-class RepositoryError(Error):
-  """Indicate an error with a repository's state, such as a missing file."""
+class BadVersionNumberError(RepositoryError):
+  """Indicate an error for metadata that contains an invalid version number."""
 
 
 class MissingLocalRepositoryError(RepositoryError):
@@ -119,36 +117,29 @@ class ForbiddenTargetError(RepositoryError):
   """Indicate that a role signed for a target that it was not delegated to."""
 
 
-class ExpiredMetadataError(Error):
+class ExpiredMetadataError(RepositoryError):
   """Indicate that a TUF Metadata file has expired."""
 
 
 class ReplayedMetadataError(RepositoryError):
   """Indicate that some metadata has been replayed to the client."""
 
-  def __init__(self, metadata_role, previous_version, current_version):
+  def __init__(self, metadata_role, downloaded_version, current_version):
     super(ReplayedMetadataError, self).__init__()
 
     self.metadata_role = metadata_role
-    self.previous_version = previous_version
+    self.downloaded_version = downloaded_version
     self.current_version = current_version
 
-
   def __str__(self):
     return (
         'Downloaded ' + repr(self.metadata_role) + ' is older (' +
-        repr(self.previous_version) + ') than the version currently '
+        repr(self.downloaded_version) + ') than the version currently '
         'installed (' + repr(self.current_version) + ').')
 
   def __repr__(self):
     return self.__class__.__name__ + ' : ' + str(self)
 
-    # # Directly instance-reproducing:
-    # return (
-    #     self.__class__.__name__ + '(' + repr(self.metadata_role) + ', ' +
-    #     repr(self.previous_version) + ', ' + repr(self.current_version) + ')')
-
-
 
 class CryptoError(Error):
   """Indicate any cryptography-related errors."""
@@ -250,7 +241,7 @@ class InvalidNameError(Error):
   """Indicate an error while trying to validate any type of named object."""
 
 
-class UnsignedMetadataError(Error):
+class UnsignedMetadataError(RepositoryError):
   """Indicate metadata object with insufficient threshold of signatures."""
 
   def __init__(self, message, signable):