Exception cleanup

Introduce djrill.NotSupportedByMandrillError for unsupported functionality (previously used generic ValueError).
Change to djrill.MandrillAPIError, derived from requests.HTTPError, for API error responses (previously used djrill.mail.backends.djrill.DjrillBackendHTTPError -- retained as equivalent for backwards compatibility).

djrill/exceptions.py

@@ -0,0 +1,33 @@
+from requests import HTTPError
+
+class MandrillAPIError(HTTPError):
+    """Exception for unsuccessful response from Mandrill API."""
+    def __init__(self, status_code, response=None, log_message=None):
+        super(MandrillAPIError, self).__init__()
+        self.status_code = status_code
+        self.response = response # often contains helpful Mandrill info
+        self.log_message = log_message
+
+    def __str__(self):
+        message = "Mandrill API response %d" % self.status_code
+        if self.log_message:
+            message += "\n" + self.log_message
+        if self.response:
+            message += "\nResponse: " + getattr(self.response, 'content', "")
+        return message
+
+
+class NotSupportedByMandrillError(ValueError):
+    """Exception for email features that Mandrill doesn't support.
+
+    This is typically raised when attempting to send a Django EmailMessage that
+    uses options or values you might expect to work, but that are silently
+    ignored by or can't be communicated to Mandrill's API. (E.g., unsupported
+    attachment types, multiple bcc recipients.)
+
+    It's generally *not* raised for Mandrill-specific features, like limitations
+    on Mandrill tag names or restrictions on from emails. (Djrill expects
+    Mandrill to return an API error for these where appropriate, and tries to
+    avoid duplicating Mandrill's validation logic locally.)
+
+    """