Replace ABCMeta with just ABC

aiohttp/abc.py

@@ -1,20 +1,20 @@
 import asyncio
 import sys
-from abc import ABCMeta, abstractmethod
+from abc import ABC, abstractmethod
 
 
 PY_35 = sys.version_info >= (3, 5)
 
 
-class AbstractRouter(metaclass=ABCMeta):
+class AbstractRouter(ABC):
 
     @asyncio.coroutine  # pragma: no branch
     @abstractmethod
     def resolve(self, request):
         """Return MATCH_INFO for given request"""
 
 
-class AbstractMatchInfo(metaclass=ABCMeta):
+class AbstractMatchInfo(ABC):
 
     @asyncio.coroutine  # pragma: no branch
     @abstractmethod
@@ -36,7 +36,7 @@ def get_info(self):
         """Return a dict with additional info useful for introspection"""
 
 
-class AbstractView(metaclass=ABCMeta):
+class AbstractView(ABC):
 
     def __init__(self, request):
         self._request = request

aiohttp/protocol.py

@@ -7,7 +7,7 @@
 import string
 import sys
 import zlib
-from abc import abstractmethod, ABCMeta
+from abc import abstractmethod, ABC
 from wsgiref.handlers import format_date_time
 
 import aiohttp
@@ -481,7 +481,7 @@ def filter_pipe(filter, filter2, *,
         chunk = yield EOL_MARKER
 
 
-class HttpMessage(metaclass=ABCMeta):
+class HttpMessage(ABC):
     """HttpMessage allows to write headers and payload to a stream.
 
     For example, lets say we want to read file then compress it with deflate

aiohttp/web_urldispatcher.py

@@ -66,7 +66,7 @@ def _append_query(url, query):
             return url
 
 
-class AbstractRoute(metaclass=abc.ABCMeta):
+class AbstractRoute(abc.ABC):
     METHODS = hdrs.METH_ALL | {hdrs.METH_ANY}
 
     def __init__(self, method, handler, *,