diff --git a/fluent/asynchandler.py b/fluent/asynchandler.py
index e150383..397608e 100644
--- a/fluent/asynchandler.py
+++ b/fluent/asynchandler.py
@@ -1,5 +1,4 @@
-from fluent import asyncsender
-from fluent import handler
+from fluent import asyncsender, handler
 
 
 class FluentHandler(handler.FluentHandler):
diff --git a/fluent/asyncsender.py b/fluent/asyncsender.py
index 73a1e61..b391290 100644
--- a/fluent/asyncsender.py
+++ b/fluent/asyncsender.py
@@ -1,5 +1,5 @@
 import threading
-from queue import Queue, Full, Empty
+from queue import Empty, Full, Queue
 
 from fluent import sender
 from fluent.sender import EventTime
diff --git a/fluent/handler.py b/fluent/handler.py
index 2bc42b4..1018d69 100644
--- a/fluent/handler.py
+++ b/fluent/handler.py
@@ -76,7 +76,7 @@ def __init__(
                 self._formatter = self._format_by_dict
                 self.usesTime = self._format_by_dict_uses_time
             else:
-                if hasattr(fmt, "__call__"):
+                if callable(fmt):
                     self._formatter = fmt
                     self.usesTime = fmt.usesTime
                 else:
diff --git a/tests/test_asyncsender.py b/tests/test_asyncsender.py
index d690ae1..a16c43f 100644
--- a/tests/test_asyncsender.py
+++ b/tests/test_asyncsender.py
@@ -1,4 +1,3 @@
-import socket
 import unittest
 
 import msgpack
@@ -122,13 +121,13 @@ def test_no_last_error_on_successful_emit(self):
 
     def test_last_error_property(self):
         EXCEPTION_MSG = "custom exception for testing last_error property"
-        self._sender.last_error = socket.error(EXCEPTION_MSG)
+        self._sender.last_error = OSError(EXCEPTION_MSG)
 
         self.assertEqual(self._sender.last_error.args[0], EXCEPTION_MSG)
 
     def test_clear_last_error(self):
         EXCEPTION_MSG = "custom exception for testing clear_last_error"
-        self._sender.last_error = socket.error(EXCEPTION_MSG)
+        self._sender.last_error = OSError(EXCEPTION_MSG)
         self._sender.clear_last_error()
 
         self.assertEqual(self._sender.last_error, None)
@@ -141,7 +140,7 @@ def test_connect_exception_during_sender_init(self, mock_socket):
         # Make the socket.socket().connect() call raise a custom exception
         mock_connect = mock_socket.socket.return_value.connect
         EXCEPTION_MSG = "a sender init socket connect() exception"
-        mock_connect.side_effect = socket.error(EXCEPTION_MSG)
+        mock_connect.side_effect = OSError(EXCEPTION_MSG)
 
         self.assertEqual(self._sender.last_error.args[0], EXCEPTION_MSG)
 
diff --git a/tests/test_event.py b/tests/test_event.py
index 6e2f0a0..1e597d8 100644
--- a/tests/test_event.py
+++ b/tests/test_event.py
@@ -28,7 +28,7 @@ def test_logging_with_timestamp(self):
         # XXX: This tests succeeds even if the fluentd connection failed
 
         # send event with tag app.follow, with timestamp
-        event.Event("follow", {"from": "userA", "to": "userB"}, time=int(0))
+        event.Event("follow", {"from": "userA", "to": "userB"}, time=0)
 
     def test_no_last_error_on_successful_event(self):
         global_sender = sender.get_global_sender()
diff --git a/tests/test_sender.py b/tests/test_sender.py
index d915e98..69d09ed 100644
--- a/tests/test_sender.py
+++ b/tests/test_sender.py
@@ -1,5 +1,4 @@
 import errno
-import socket
 import sys
 import unittest
 from shutil import rmtree
@@ -121,13 +120,13 @@ def test_no_last_error_on_successful_emit(self):
 
     def test_last_error_property(self):
         EXCEPTION_MSG = "custom exception for testing last_error property"
-        self._sender.last_error = socket.error(EXCEPTION_MSG)
+        self._sender.last_error = OSError(EXCEPTION_MSG)
 
         self.assertEqual(self._sender.last_error.args[0], EXCEPTION_MSG)
 
     def test_clear_last_error(self):
         EXCEPTION_MSG = "custom exception for testing clear_last_error"
-        self._sender.last_error = socket.error(EXCEPTION_MSG)
+        self._sender.last_error = OSError(EXCEPTION_MSG)
         self._sender.clear_last_error()
 
         self.assertEqual(self._sender.last_error, None)
@@ -225,12 +224,12 @@ def __init__(self):
                     self.send_side_effects = [3, 0, 9]
                     self.send_idx = 0
                     self.recv_side_effects = [
-                        socket.error(errno.EWOULDBLOCK, "Blah"),
+                        OSError(errno.EWOULDBLOCK, "Blah"),
                         b"this data is going to be ignored",
                         b"",
-                        socket.error(errno.EWOULDBLOCK, "Blah"),
-                        socket.error(errno.EWOULDBLOCK, "Blah"),
-                        socket.error(errno.EACCES, "This error will never happen"),
+                        OSError(errno.EWOULDBLOCK, "Blah"),
+                        OSError(errno.EWOULDBLOCK, "Blah"),
+                        OSError(errno.EACCES, "This error will never happen"),
                     ]
                     self.recv_idx = 0