Cleanup: simplify requests backend raise_for_status

Treat all 2xx (not just 200) as success in base
AnymailRequestsBackend.raise_for_status, eliminating
some unnecessary subclass overrides.

anymail/backends/base_requests.py

@@ -87,9 +87,10 @@ def raise_for_status(self, response, payload, message):
         (though should defer parsing/deserialization of the body to
         parse_recipient_status)
         """
-        if response.status_code != 200:
-            raise AnymailRequestsAPIError(email_message=message, payload=payload, response=response,
-                                          backend=self)
+        if response.status_code < 200 or response.status_code >= 300:
+            raise AnymailRequestsAPIError(
+                email_message=message, payload=payload,
+                response=response, backend=self)
 
     def deserialize_json_response(self, response, payload, message):
         """Deserialize an ESP API response that's in json.

anymail/backends/sendgrid.py

@@ -5,7 +5,7 @@
 from requests.structures import CaseInsensitiveDict
 
 from .base_requests import AnymailRequestsBackend, RequestsPayload
-from ..exceptions import AnymailConfigurationError, AnymailRequestsAPIError, AnymailWarning
+from ..exceptions import AnymailConfigurationError, AnymailWarning
 from ..message import AnymailRecipientStatus
 from ..utils import BASIC_NUMERIC_TYPES, Mapping, get_anymail_setting, update_deep
 
@@ -52,11 +52,6 @@ def __init__(self, **kwargs):
     def build_message_payload(self, message, defaults):
         return SendGridPayload(message, defaults, self)
 
-    def raise_for_status(self, response, payload, message):
-        if response.status_code < 200 or response.status_code >= 300:
-            raise AnymailRequestsAPIError(email_message=message, payload=payload, response=response,
-                                          backend=self)
-
     def parse_recipient_status(self, response, payload, message):
         # If we get here, the send call was successful.
         # (SendGrid uses a non-2xx response for any failures, caught in raise_for_status.)

anymail/backends/sendinblue.py

@@ -35,15 +35,6 @@ def __init__(self, **kwargs):
     def build_message_payload(self, message, defaults):
         return SendinBluePayload(message, defaults, self)
 
-    def raise_for_status(self, response, payload, message):
-        if response.status_code < 200 or response.status_code >= 300:
-            raise AnymailRequestsAPIError(
-                email_message=message,
-                payload=payload,
-                response=response,
-                backend=self,
-            )
-
     def parse_recipient_status(self, response, payload, message):
         # SendinBlue doesn't give any detail on a success
         # https://developers.sendinblue.com/docs/responses