diff --git a/.travis.yml b/.travis.yml
index 8ab6316..3bf010e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,7 +1,7 @@
 language: python
 
 python:
-  - "2.7"
+  - "3.5"
 
 install: "pip install -r requirements.txt"
 
diff --git a/src/app.py b/src/app.py
index 644ee6a..07ae6b4 100644
--- a/src/app.py
+++ b/src/app.py
@@ -1,3 +1,5 @@
+#!/usr/bin/env python3
+
 import json
 import logging
 import os
@@ -10,14 +12,12 @@ log.init()
 logger = logging.getLogger('app')
 
 
-def get_or_raise(env):
+def get_or_raise(env: str) -> str:
     """
     Check if needed environment variables are given.
 
     :param env: key
-    :type env: str
     :return: value
-    :rtype: str
     """
     env_value = os.getenv(env)
     if not env_value:
@@ -26,14 +26,12 @@ def get_or_raise(env):
     return env_value
 
 
-def str_to_bool(str):
+def str_to_bool(str: str) -> bool:
     """
     Convert string to boolean.
 
     :param str: given string
-    :type str: str
     :return: converted string
-    :rtype: bool
     """
     try:
         return str.lower() in ('yes', 'true', 't', '1')
@@ -54,14 +52,12 @@ logger.info('Android version: {version} \n'
                                          img=SYS_IMG))
 
 
-def prepare_avd(device, avd_name):
+def prepare_avd(device: str, avd_name: str):
     """
     Create and run android virtual device.
 
     :param device: Device name
-    :type device: str
     :param avd_name: Name of android virtual device / emulator
-    :type avd_name: str
     """
     cmd = 'echo no | android create avd -f -n {name} -t android-{api} -b {sys_img}'.format(
         name=avd_name, api=API_LEVEL, sys_img=SYS_IMG)
@@ -95,12 +91,11 @@ def prepare_avd(device, avd_name):
     subprocess.check_call('xterm -T "{titel}" -n "{titel}" -e \"{cmd}\"'.format(titel=titel, cmd=cmd), shell=True)
 
 
-def appium_run(avd_name):
+def appium_run(avd_name: str):
     """
     Run appium server.
 
     :param avd_name: Name of android virtual device / emulator
-    :type avd_name: str
     """
     cmd = 'appium'
 
@@ -120,21 +115,15 @@ def appium_run(avd_name):
     subprocess.check_call('xterm -T "{titel}" -n "{titel}" -e \"{cmd}\"'.format(titel=titel, cmd=cmd), shell=True)
 
 
-def create_node_config(avd_name, appium_host, appium_port, selenium_host, selenium_port):
+def create_node_config(avd_name: str, appium_host: str, appium_port: int, selenium_host: str, selenium_port: int):
     """
     Create custom node config file in json format to be able to connect with selenium server.
 
     :param avd_name: Name of android virtual device / emulator
-    :type avd_name: str
     :param appium_host: Host where appium server is running
-    :type appium_host: str
     :param appium_port: Port number where where appium server is running
-    :type appium_port: int
     :param selenium_host: Host where selenium server is running
-    :type selenium_host: str
     :param selenium_port: Port number where selenium server is running
-    :type selenium_port: int
-
     """
     config = {
         'capabilities': [
diff --git a/src/log.py b/src/log.py
index ac9b1da..36cf476 100644
--- a/src/log.py
+++ b/src/log.py
@@ -5,4 +5,5 @@ from src import LOGGING_FILE
 
 
 def init():
+    """Init log."""
     logging.config.fileConfig(LOGGING_FILE)
diff --git a/supervisord.conf b/supervisord.conf
index 975f672..76c39a8 100644
--- a/supervisord.conf
+++ b/supervisord.conf
@@ -24,7 +24,7 @@ stdout_logfile=%(ENV_LOG_PATH)s/novnc.log
 redirect_stderr=true
 
 [program:docker-appium]
-command=python -m src.app
+command=python3 -m src.app
 autorestart=false
 stdout_logfile=%(ENV_LOG_PATH)s/docker-appium.log
 redirect_stderr=true