diff --git a/testgres/testgres.py b/testgres/testgres.py
index d40d51fa..2bcbbd4f 100644
--- a/testgres/testgres.py
+++ b/testgres/testgres.py
@@ -23,7 +23,7 @@
 
 import os
 import random
-import socket
+# import socket
 import subprocess
 import pwd
 import tempfile
@@ -31,7 +31,7 @@
 import time
 import six
 
-# Try to use psycopg2 by default. If psycopg2 isn"t available then use 
+# Try to use psycopg2 by default. If psycopg2 isn"t available then use
 # pg8000 which is slower but much more portable because uses only
 # pure-Python code
 try:
@@ -44,21 +44,28 @@
 
 
 registered_nodes = []
-last_assigned_port = int(random.random() * 16384) + 49152;
+last_assigned_port = int(random.random() * 16384) + 49152
 pg_config_data = {}
 
 
-"""
-Predefined exceptions
-"""
-class ClusterException(Exception): pass
-class QueryException(Exception): pass
+class ClusterException(Exception):
+    """
+    Predefined exceptions
+    """
+    pass
+
+
+class QueryException(Exception):
+    """
+    Predefined exceptions
+    """
+    pass
 
 
-"""
-Transaction wrapper returned by Node
-"""
 class NodeConnection(object):
+    """
+    Transaction wrapper returned by Node
+    """
     def __init__(self, parent_node, dbname):
         self.parent_node = parent_node
 
@@ -78,21 +85,22 @@ def __exit__(self, type, value, tb):
         self.connection.close()
 
     def begin(self, isolation_level=0):
-        levels = [ 'read uncommitted',
-                   'read committed',
-                   'repeatable read',
-                   'serializable' ]
+        levels = ['read uncommitted',
+                  'read committed',
+                  'repeatable read',
+                  'serializable']
 
+        print(type(isolation_level))
         # Check if level is int [0..3]
-        if isinstance(isolation_level, int) and \
-           isolation_level in range(0, 4):
+        if (isinstance(isolation_level, int) and
+           isolation_level in range(0, 4)):
 
             # Replace index with isolation level type
             isolation_level = levels[isolation_level]
 
         # Or it might be a string
-        elif isinstance(isolation_level, str) and \
-             str.lower(isolation_level) in levels:
+        elif (isinstance(isolation_level, six.text_type) and
+              isolation_level.lower() in levels):
 
             # Nothing to do here
             pass
@@ -148,13 +156,13 @@ def error_filename(self):
 
     @property
     def connstr(self):
-        return "port=%s" % self.port    
+        return "port=%s" % self.port
         # return "port=%s host=%s" % (self.port, self.host)
 
     def get_bin_path(self, filename):
         """ Returns full path to an executable """
         pg_config = get_config()
-        if not "BINDIR" in pg_config:
+        if "BINDIR" not in pg_config:
             return filename
         else:
             return "%s/%s" % (pg_config.get("BINDIR"), filename)
@@ -403,6 +411,7 @@ def get_username():
     """ Returns current user name """
     return pwd.getpwuid(os.getuid())[0]
 
+
 def get_config():
     global pg_config_data
 
@@ -422,6 +431,7 @@ def get_config():
 
     return pg_config_data
 
+
 def version_to_num(version):
     """Converts PostgreSQL version to number for easier comparison"""
     import re
@@ -429,12 +439,14 @@ def version_to_num(version):
     if not version:
         return 0
     parts = version.split(".")
-    while len(parts) < 3: parts.append("0")
+    while len(parts) < 3:
+        parts.append("0")
     num = 0
     for part in parts:
         num = num*100 + int(re.sub("[^\d]", "", part))
     return num
 
+
 def get_new_node(name):
     global registered_nodes
     global last_assigned_port
@@ -462,12 +474,14 @@ def get_new_node(name):
 
     return node
 
+
 def clean_all():
     global registered_nodes
     for node in registered_nodes:
         node.cleanup()
     registered_nodes = []
 
+
 def stop_all():
     global registered_nodes
     for node in registered_nodes:
diff --git a/testgres/tests/test_simple.py b/testgres/tests/test_simple.py
index 76838886..e59be4be 100644
--- a/testgres/tests/test_simple.py
+++ b/testgres/tests/test_simple.py
@@ -1,6 +1,8 @@
 import unittest
-import time
-from testgres import get_new_node, clean_all, stop_all
+# import time
+# from testgres import clean_all
+from testgres import get_new_node, stop_all
+
 
 class SimpleTest(unittest.TestCase):