extensions: Use intended base exception class.

caucase/exceptions.py

@@ -20,16 +20,16 @@ class CertificateAuthorityException(Exception):
   """Base exception"""
   pass
 
-class NoStorage(Exception):
+class NoStorage(CertificateAuthorityException):
   """No space in storage"""
   pass
 
-class NotFound(Exception):
+class NotFound(CertificateAuthorityException):
   """Requested resource does not exist"""
   pass
 
-class Found(Exception):
+class Found(CertificateAuthorityException):
   """Requested ID is already in use"""
 
-class BadSignature(Exception):
+class BadSignature(CertificateAuthorityException):
   """Non-x509 signature check failed"""