Fix RSA object usage in type hints

It seems little-boxes replaced our crypto library which caused
a bit of a mayhem since some of the internal objects don't match.
If we need that library after all, will need to drop these type
hints.

federation/outbound.py

@@ -2,7 +2,7 @@ import json
 import logging
 from typing import List, Tuple, Union
 
-from Crypto.PublicKey.RSA import RsaKey
+from Crypto.PublicKey.RSA import _RSAobj
 
 from federation.entities.diaspora.mappers import get_outbound_entity
 from federation.entities.mixins import BaseEntity
@@ -15,7 +15,7 @@ logger = logging.getLogger("federation")
 
 
 def handle_create_payload(
-        entity:BaseEntity, author_user:UserType, to_user_key:RsaKey=None, parent_user:UserType=None) -> str:
+        entity:BaseEntity, author_user:UserType, to_user_key:_RSAobj=None, parent_user:UserType=None) -> str:
     """Create a payload with the correct protocol.
 
     Any given user arguments must have ``private_key`` and ``handle`` attributes.
@@ -41,7 +41,7 @@ def handle_create_payload(
 def handle_send(
         entity: BaseEntity,
         author_user: UserType,
-        recipients: List[Union[Tuple[str, RsaKey], str]]=None,
+        recipients: List[Union[Tuple[str, _RSAobj], str]]=None,
         parent_user: UserType=None,
 ) -> None:
     """Send an entity to remote servers.

federation/protocols/diaspora/protocol.py

@@ -4,7 +4,7 @@ from base64 import urlsafe_b64decode
 from typing import Callable, Tuple, Union, Dict
 from urllib.parse import unquote
 
-from Crypto.PublicKey.RSA import RsaKey
+from Crypto.PublicKey.RSA import _RSAobj
 from lxml import etree
 
 from federation.entities.mixins import BaseEntity
@@ -122,7 +122,7 @@ class Protocol:
             raise NoSenderKeyFoundError("Could not find a sender contact to retrieve key")
         MagicEnvelope(doc=self.doc, public_key=sender_key, verify=True)
 
-    def build_send(self, entity:BaseEntity, from_user:UserType, to_user_key:RsaKey=None) -> Union[str, Dict]:
+    def build_send(self, entity:BaseEntity, from_user:UserType, to_user_key:_RSAobj=None) -> Union[str, Dict]:
         """
         Build POST data for sending out to remotes.