Fix aiohttp typing

Author: lmazuel

msrest/universal_http/__init__.py

@@ -40,7 +40,7 @@
     from urllib.parse import urlparse
 import xml.etree.ElementTree as ET
 
-from typing import TYPE_CHECKING, Generic, TypeVar, cast, IO, List, Union, Any, Mapping, Dict, Optional, Tuple, Callable, Iterator  # pylint: disable=unused-import
+from typing import TYPE_CHECKING, Generic, TypeVar, cast, IO, List, Union, Any, Mapping, Dict, Optional, Tuple, Callable, Iterator, MutableMapping  # pylint: disable=unused-import
 
 HTTPResponseType = TypeVar("HTTPResponseType", bound='HTTPClientResponse')
 
@@ -325,7 +325,7 @@ def __init__(self, request, internal_response):
         self.request = request
         self.internal_response = internal_response
         self.status_code = None  # type: Optional[int]
-        self.headers = {}  # type: Dict[str, str]
+        self.headers = {}  # type: MutableMapping[str, str]
         self.reason = None  # type: Optional[str]
 
     def body(self):

msrest/universal_http/aiohttp.py

@@ -26,6 +26,7 @@
 from typing import Any, Callable, AsyncIterator, Optional
 
 import aiohttp
+from multidict import CIMultiDict
 
 from . import AsyncHTTPSender, ClientRequest, AsyncClientResponse
 
@@ -69,7 +70,7 @@ def __init__(self, request: ClientRequest, aiohttp_response: aiohttp.ClientRespo
         super(AioHttpClientResponse, self).__init__(request, aiohttp_response)
         # https://aiohttp.readthedocs.io/en/stable/client_reference.html#aiohttp.ClientResponse
         self.status_code = aiohttp_response.status
-        self.headers = aiohttp_response.headers
+        self.headers = CIMultiDict(aiohttp_response.headers)
         self.reason = aiohttp_response.reason
         self._body = None