Add two new exceptions for handling MRO error cases.

DuplicateBasesError is emitted when duplicate bases are found in a class,
InconsistentMroError is raised when the method resolution is determined
to be inconsistent. They share a common class, MroError, which
is a subclass of ResolveError, meaning that this change is backwards compatible.

1 files changed, 12 insertions, 0 deletions

diff --git a/astroid/exceptions.py b/astroid/exceptions.py
index 3889e2e..d1094ce 100644
--- a/astroid/exceptions.py
+++ b/astroid/exceptions.py
@@ -30,6 +30,18 @@ class AstroidBuildingException(AstroidError):
 class ResolveError(AstroidError):
     """base class of astroid resolution/inference error"""
 
+class MroError(ResolveError):
+    """Error raised when there is a problem with method resolution of a class."""
+
+
+class DuplicateBasesError(MroError):
+    """Error raised when there are duplicate bases in the same class bases."""
+
+
+class InconsistentMroError(MroError):
+    """Error raised when a class's MRO is inconsistent."""
+
+
 class NotFoundError(ResolveError):
     """raised when we are unable to resolve a name"""