Fix logger report for unix socket

aiohttp/helpers.py

@@ -345,8 +345,13 @@ def _format_o(key, args):
 
     @staticmethod
     def _format_a(args):
-        return args[3].get_extra_info('peername')[0] if args[3] is not None \
-            else '-'
+        if args[3] is None:
+            return '-'
+        peername = args[3].get_extra_info('peername')
+        if isinstance(peername, (list, tuple)):
+            return peername[0]
+        else:
+            return peername
 
     @staticmethod
     def _format_t(args):

tests/test_helpers.py

@@ -176,6 +176,21 @@ def test_access_logger_dicts():
     mock_logger.info.assert_called_with(expected)
 
 
+def test_access_logger_unix_socket():
+    log_format = '|%a|'
+    mock_logger = mock.Mock()
+    access_logger = helpers.AccessLogger(mock_logger, log_format)
+    message = mock.Mock(headers={"User-Agent": "Mock/1.0"}, version=(1, 1))
+    environ = {}
+    response = mock.Mock()
+    transport = mock.Mock()
+    transport.get_extra_info.return_value = ""
+    access_logger.log(message, environ, response, transport, 0.0)
+    assert not mock_logger.error.called
+    expected = '||'
+    mock_logger.info.assert_called_with(expected)
+
+
 def test_logger_no_message_and_environ():
     mock_logger = mock.Mock()
     mock_transport = mock.Mock()