[Draft] Add exception handler for better exp

Author: pratapaprasanna

authenticator/exceptions.py

@@ -0,0 +1,64 @@
+import Exception
+import oauthlib
+
+from oslo_log import log as logging
+
+oauthlib.oauth2.rfc6749.errors.InvalidGrantError
+
+
+class OauthException(Exception):
+    """
+    Base Oauth Exception class
+    To correctly use this class, inherit from it and define
+    a 'msg_fmt' property. That msg_fmt will get printf'd
+    with the keyword arguments provided to the constructor.
+    """
+
+    msg_fmt = _("An unknown exception occurred.")
+    code = 500
+    headers = {}
+    safe = False
+
+    def __init__(self, message=None, **kwargs):
+        self.kwargs = kwargs
+
+        if "code" not in self.kwargs:
+            try:
+                self.kwargs["code"] = self.code
+            except AttributeError:
+                pass
+
+        try:
+            if not message:
+                message = self.msg_fmt % kwargs
+            else:
+                message = str(message)
+        except Exception:
+            # NOTE(melwitt): This is done in a separate method so it can be
+            # monkey-patched during testing to make it a hard failure.
+            self._log_exception()
+            message = self.msg_fmt
+
+        self.message = message
+        super(NovaException, self).__init__(message)
+
+    def _log_exception(self):
+        # kwargs doesn't match a variable in the message
+        # log the issue and the kwargs
+        LOG.exception("Exception in string format operation")
+        for name, value in self.kwargs.items():
+            LOG.error("%s: %s" % (name, value))  # noqa
+
+    def format_message(self):
+        # NOTE(mrodden): use the first argument to the python Exception object
+        # which should be our full NovaException message, (see __init__)
+        return self.args[0]
+
+    def __repr__(self):
+        dict_repr = self.__dict__
+        dict_repr["class"] = self.__class__.__name__
+        return str(dict_repr)
+
+
+class EncryptionFailure(NovaException):
+    msg_fmt = _("Failed to encrypt text: %(reason)s")